Because most emotionally mature adults can separate truth that's provable from "truth" that is entirely subjective and completely unprovable. I'll clue you in AlwaysThere. Most people don't really care all that much about what kinds of fantasy stories either Muslims or Christians (or religious people of whatever faith) have thought up over the centuries. Most people bank on what they can demonstrate to be true--gravity, the earth revolving around the sun, anything having mass has an equivalent amount of energy, etc. and not questions like whether some 1st century prophet is a god or an ordinary man. Really, few modern educated humans give metaphysical questions much thought. They're more worried about provable things like aging and concrete problems such as what they're going to do when the Republican party destroys Medicare.