>>77036381It's just a thing that occurred over time. People kept pushing the envelope with how much of the boob they'd show. People would scream about it being obscene but the line between what counts as boob and what is just neck is impossible to define.
However, the difference between boob and tit IS easy to define, so that kind of naturally became the point of "ok, just don't show naked nipples".
Think about it, if they say "alright so you can show 25% of the boob before it becomes lewd" people just draw the boobs larger. The only way to define it is as clear points like tit, buttcrack, frontcrack, etc.
