I grew up in a fairly open family where I wasn't worried someone would come barging in if I didn't lock the bathroom door and also felt it wasn't a huge deal to not latch the door completely. Everyone respected each other's privacy and bodily functions were definitely never something to be ashamed of.
That said, in the past, after getting comfortable with a boyfriend, peeing with the door open wasn't a huge deal, however with Marco...
...we always shut the door. A rule he enforces and something I appreciate after a couple years together. It keeps something very normal and simple private, but on the flip side, protects the sexy image you have of one another.
I know this isn't for everyone, and with friends, we seem to be the minority, but, I'd love to hear your thoughts; sound off in the comments below!