On rare occasion, you will see people crossing boundaries but for the most part, people don't cross that line. They know it's a line they don't cross....even if temptation(s) calls for it. Ex: over the weekend, I see a slim beautiful woman w/ an elderly man. I noticed her and I'm sure other guys will too. I'm sure some guys are drooling but no one is doing anything because they know there's a boundary they don't cross...
However if she's single, i'm sure guys will be flocking to her haha...
It's called having self-discipline. Some people don't have it.
I was telling Reporter in another thread that only people who are looking for action will notice/sense/perceive others hitting on them. When you no longer seek out such things, you won't even notice that someone is flirting with you. In order to notice, that other person would have to be super obvious and very aggressive.