Oh, I understand what you're saying, but someone on these forums pointed out to me years ago, and it stuck with me, that existance of gods or god-like beings still doesn't mandate worship, because of all the other god-like beings running around, like wizards, or Clerics of philosophies instead of deities (which some DMs don't allow, I know), or Bards who can heal, too.
In other words, unless you do have beings who smite you if you so much as get their name or doctrine wrong, which bring its own different set of campaign problems, then because of the nature of mortals, and humans in particular, you WILL get different gods, sects, names, and heresies for even the exact same beings over thousands of years. That an Elf will call Bahamut "Bahamut" and a human will call him "Bahamut" doesn't ring my credibility bell.
(Then again, they probably wouldn't be using the same currency, either, but that's for another thread.)
Again, for the default game, it's fine - D&D out of the box, so to speak, needs some conventions to make it play, and if that includes a unified currency, religious pantheon, and languages, then so be it.