Plus, maybe they've never been checked and were born with something, you never know. So it's always good to want to know, and I actually have asked personally for every partner I had up until I met hubby. If I didn't know they were clean I didn't want to have sex with them. It was just because of how paranoid I am to get something, and if they had something I wanted to know how to take precautions.
No one has EVER minded and no one has EVER objected