What kind of shower curtain/door do you have? Would you consider it odd for someone else to use the bathroom or just come in to talk to you while you're showering?
My answers: My home bathroom door doesn't lock, so no. I do tend to lock it at other peoples' houses though.
Opaque beige shower curtain. Six people in a one-bathroom house (five of us are girls) growing up means I'm comfortable with people using the bathroom while I'm showering and vice versa.