I didn't start until we were in the middle of bathroom renos. The upstairs bathroom is the only one with a shower, so during renos the toilet and sink were removed, and I'd have to run downstairs to pee, then come back up to shower, then go back down to pee again after shower.
When I was in middle school, I remember staying up late waiting on my sister to get home from the airport and watching a late night interview with Madonna. They talked about peeing in the shower. I never did it before that, but that seemed to make it less weird. I only do it occasionally if I don't pee before I get in and then don't want to get out and come back.
I only remember peeing in the shower once and it was when I was in college. I got in the shower without peeing and then I was like oh no I have to pee and panicked a little until I realized I could just pee in the shower lol.
I have nothing against peeing in showers though. If you gotta go you gotta go