Why would God...?

Questions that begin in this way are notoriously hard to answer, and there's no shame in answering many of these questions with an honest, "I've no idea." The Bible does say that God's ways are past finding out. It ought to come as no surprise that there are things God does and allows that we don't understand. However, the question I recently heard asked does not fall into that category.

Why would God allow rebellion to continue forever in hell? Why not bring it to an end by annihilating people?

This question is one which can be answered in a couple of ways. First, this question displays an attitude of "The end justifies the means." The reasoning goes like this, "God wouldn't want rebellion going on forever, so why doesn't He use His power to make it stop?" But might doesn't make right, and just because God can do something doesn't mean He should do it. J. P. Moreland makes the point well:

Believe it or not, everlasting separation from God is morally superior to annihilation...Why would God be morally justified in annihilating somebody? The only way that's a good thing would be the end result, which would be to keep people from experiencing the conscious separation from God forever [or to stop them rebelling against God forever]. Well, then you're treating people as a means to an end.

It's like forcing people to go to heaven. What you're saying is, "The thing that really matters is that people no longer suffer consciously, so I'm going to achieve that end." Do you see? That's treating the person as a means to an end. What hell does is recognise that people have intrinsic value. If God loves intrinsic value, then He has got to be a sustainer of persons, because that means He is a sustainer of intrinsic value. He refuses to snuff out a creature that was made in His own image. So in the final analysis, hell is the only morally legitimate option. (The Case for Faith, Lee Strobel)

God doesn't like rebellion, but He won't just snuff people out because of that.

The second reason is because it means people escape the punishment for their sins. If people have rebelled against God then they deserve punishment for that. The Bible is crystal clear that conscious suffering is the punishment for sin. Now, because we are finite creatures we can never pay the infinite penalty our sins deserve and God's law demands. Furthermore, because of the sinner's ongoing rebellion they continually merit more suffering. God would be unrighteous if He just brought that to an end, and if God could fudge on justice and bring the suffering of a sinner to an end before he has paid the penalty, then why does He allow the suffering to begin? If God doesn't demand justice to be done then why does He allow the sinner to suffer at all? And if someone thinks that sinners won't suffer for his sins then he can't even pretend to be a Bible believer.

Make no mistake about it, those who never have their sins forgiven through faith in Christ will suffer for their sins, and it will never be brought to an end.

I have more on this in He that believeth not... for anyone who wants to explore this issues in greater depth.