And where it does exist, it’s usually someone exploiting power and/or access to another person, e.g. superiors in the workplace taking advantage of subordinates, customers being inappropriate to servers and not understanding or caring that it’s their job to serve them and their advances are not welcome, that weird/obsessed guy in your greater friend circle that you never want to be alone with, etc.
Respectful advances in places where both people are on equal footing and there are not external pressures, have never been seen as off limits as far as I am aware.