They still have housemothers. At colleges and GLOs that are definitely not restricted to "religious" or "Christian" members.
http://family.auburn.edu/profiles/bl...frat-house-mom
http://www.alligator.org/news/local/...9bb2963f4.html
I'm pretty sure anyone who has an issue with group showering (be it genitalia or just plain shyness) finds a way around taking a shower when everyone else is. Also, why do you automatically assume that everyone would live in the house? Many people don't, for various reasons.
And yes I've been to gyms, and I know this will shock you, but I haven't been in the men's locker room.