I always pee when I’m in the shower. However, I’ve tried
stopping the habbit but it’s no use. I suppose this is what
psychologists call “conditioning”. I believe all of us pee in the
toilet during a shower(either into the bowl or the sewage cover)
when we were kids. Don’t ask me why but we just pee. Thus, we
relate shower with pee: go shower, pee comes out. It becomes harder
to kick the habit as you grow older, I guess. I mean it’s fine if
your bathroom has a toilet bowl but if it’s one of those where the
shower room is separated from the toilet, then it’d be
unhygienic(pee will stain the bathroom floor overtime, and it’d
reek of ammonia). If it helps you, I’d asked my brother before and
he said he pees during a shower, all the time.