I believe that evangelical Christianity has embraced a sort of "Repugnant Conclusion" with respect to the priorities of the church. It is unclear whether or not this repugnant conclusion is the wrong one, but it is necessary, at minimum, to assess it honestly and examine the harm done to Christian discipleship as a result.
Before I begin that assessment, however, I should probably explain what on earth is the Repugnant Conclusion.
The Repugnant Conclusion in Utilitarian Ethics
The Repugnant Conclusion (see link for technical explanation) comes from an influential thought experiment in population ethics proposed by Derek Parfit. In a world in which some number X live lives with a highly positive value, there is some other world with Y people, where Y is significantly more than X, living less positive lives, yet the second world has a greater overall value. Eventually, through these comparisons, you arrive at the Repugnant Conclusion: the world with the highest overall utility is the one in which the greatest possible population exists with minimally valuable lives.
I reject utilitarianism, of course—I believe it to be incompatible with Christianity—so I reject the assignment of value to world-states and lives based on pleasure, pain, or utility. Consequently, this thought experiment isn't a direct problem for me, but stay with me and think about it for a minute. It's highly counterintuitive, to say the least, that you want to lower the average happiness to promote higher overall happiness. Aside from invoking infinity in the latter of these cases, it would imply that the meaningless populace in Huxley's Brave New World is in some way better than the prelapsarian perfection of Adam and Eve in Eden.
Heavenly Population Ethics
Maybe you can anticipate where I'm going with this. We, as Christians, believe that people are of indeterminately high value (I hesitate to say infinite, yet it may be closer to the truth). To quote C.S. Lewis, from The Weight of Glory, "It is a serious thing to live in a society of possible gods and goddesses, to remember that the dullest and most uninteresting person you talk to may one day be a creature which, if you saw it now, you would be strongly tempted to worship, or else a horror and a corruption such as you now meet, if at all, only in a nightmare."
There is infinite goodness or infinite badness in eternity for each of us. Sure, there may be some difference in goodness in Heaven as there are different infinities, but it is uncontroversially better to have more people in Heaven. The best possible afterlife, you might say, is the one in which the most people enjoy God in the company of the saints for eternity.
But is that afterlife—an afterlife, we might say, with the maximum number of minimally rewarded Christians—superior to one with the maximum number of maximally rewarded Christians, less one soul? That conclusion, which I think it is reasonable to accept and which, I contend, forms the basis of most serious evangelistic efforts, I term the "Heavenly Repugnant Conclusion" (important note: it might not actually be repugnant, but I have to keep the naming symmetry).
I don't know that I should deny this conclusion, at least not flippantly. I think every Christian in Heaven would gladly diminish his own reward as greatly as possible if it would save a single extra person. The perfection of the souls married to Christ in their final state would choose no other than salvific self-sacrifice. And who am I to argue with the saints redeemed and perfected by Christ?
Minimally Valuable Saints
If we accept the Heavenly Repugnant Conclusion, the orientation of the evangelical churches makes sense. We need to get people into the minimum relationship with Christ necessary to save their eternal souls. Discipleship increases the capacity of Christians to experience God now, but, unless directly related to saving more souls, it's put on the back burner. (I strongly suspect the megachurch minister or celebrity pastor are seen as the most efficient means to save souls, with the result that discipleship for anyone but their heirs apparent is low-value.) Christian service may increase my reward in Heaven, and with discipleship and sanctification increase my capacity to enjoy God as the Fount of truth, beauty, and goodness, thereby increasing the positive value of my afterlife—but that doesn't matter unless it's a byproduct of increasing the number of the saints.
Evangelicalism and its churches, then, have become expert in churning out minimally valuable saints. The cultivation of Christian disciplines and the tasks of discipleship and meaningful service are accoutrements, at best, to the main task. Ideally, these minimally decent Christians would pass their faith on to the next generation; it saves energy on evangelism. But the churches are better geared to evangelize the children after they leave the church than to raise them well in the faith.
The Devil's in the Premises
I offer that the problem is not necessarily with the Heavenly Repugnant Conclusion, but rather with the premises of evangelical evangelism. It is an immoral (and risky) venture to produce minimally valuable saints.
Here are some difficult words from the Second Person of the Trinity: "Be ye therefore perfect, even as your Father which is in heaven is perfect." No room for minimally decent Christians there. We abrogate our duty if we aim for less than perfection, even though we won't hit the mark. Our pattern is the sinless and morally perfect Christ.
Even from a pragmatic perspective, though, I think we ought to reject the utter prioritization of evangelism (usually of the "come to church with me" variety) at the expense of discipleship. Which Christian is more likely to have the savor of life, the one who has grown in her relationship with God in deep and profound ways, or the one destined to squeak into the kingdom of God "out of the fire"?
Stunted discipleship stunts evangelism. Why? Because both are the duty of the mature Christian. Growing in faith means growing in obedience to the commands of Christ, and evangelism is one such command. Discipleship also equips the believer to evangelize well, to be "ready to give a defense." Without discipleship, we're not ready for much.
Also, as I am not a Calvinist, I believe that people have the freedom to choose or reject Christ, and that their freedom does not cease after their initial choice to follow the Way. That is to say, Christians can abandon the faith. There is no neutral; there is growth in the Spirit, and there is decay. Declining to emphasize sanctification and discipleship may lead believers to make a shipwreck of their faith, resulting, after all, in a less-than-maximal number of saints.
You might argue that I'm too hard on evangelicalism, that the churches really do care about discipleship. Well, churches love metrics, and the metrics all reflect the Heavenly Repugnant Conclusion: attendance, baptisms, etc. Not that it's bad to track those things, but the lack of metrics for discipleship shows that it isn't a priority.
In summary: it is a worthy goal to get as many people into Heaven as possible, but it has led to distorted priorities in evangelicalism. We can't actually achieve a maximal heavenly population without discipleship. Maximalist saints beget more maximalist saints through discipleship-informed evangelism. More Christians come to be as a result of discipleship holding its proper place than by minimizing it in the name of doing everything possible to save the lost.