Of the erogenous zones, breasts are the ones you can see most often. It may be different in the US, but where I grew up, topless sunbathing is quite a thing and I even saw a lot of boobs in shower soap commercials at 6pm on public TV as a kid. When my kids were babies, my (now ex-) wife would also just nurse them on a park bench - which also I isn’t unusual.
Level 3 is a big part of the storyline in “The Memory Police” by Yoko Ogawa