The thing is, most RPGs ignore 'common' subject grounds for most of humanity. Notice that there aren't any business-focused RPGs, despite the importance of commerce? (Red Markets isn't out yet)
RPGs are overwhelmingly themed around speculative fiction subgenres and tropes and those revolve stories about atypical experiences - war, conflict, mystery, quests, etc. They're also meant to be fun and exciting. How do you make a game about religion fun and exciting? Most game designers would rather grab the low hanging fruit of epic quests or investigating the supernatural than try to puzzle out how to make a religious fasting ritual or pilgrimage fun in a game. I'm not saying that speculative fiction ignores religion, but games are designed to be played and that requires the interest of the players. It's very hard to make business fun, which is why it has been ignored. Religion, is not perceived to be fun or exciting by most gamers. I think that's why it's been treated like it has been in games.
I kind of think their is design space for a game on the subject. I think I have a cool setting to explore it into.
Thew core dynamic goes something like.
1. Call on gods to help in settling vendetta. Go to step 2.
2. Gods expectations of worshiper become greater. Go to step 3.
3. Worshiper does something unpleasant or scandalous to appease gods. Go to step 4.
4. Worshiper incurs vendetta as a result of his actions. Go to step 1.
With the whole game telling stories of scandal, assassination, dueling and worship, in a polytheist version of renaissance Venice.
