If I had to guess, it may be because of the thought stopping nature of (some) faith-based thought. You would also need either a game studio that was willing to explore/pursue those ideas.

But you'd think with all the right wing Christian money swirling around in the US that there would be some kind of evangelizing effort through gaming.

Edit: Just remembered that Chants of Sennaar is a really cool take on the Tower of Babel concept with puzzles based on deciphering languages you don't know. So that's one interesting one.