With a few exceptions, I consider it very unprofessional for an employee or colleague of mine to start discussing their sexual preferences, gay or straight. I wouldn't ask for the same reason.

> ... just blanket “No religion/no politics” is just a way to say you like everything the way it is and don’t want to feel uncomfortable

I think you are just projecting. There are tons of benefits (mentioned elsewhere in these comments) to keeping politics & religion out of the workplace.