Why don't they get it? (Ranting)

As much as a shut in as I am, I do enjoy meeting new people. But if you're comfortable telling me I'm cute/hot/what the fuck ever and flirt when you've known me a few days or less, chances are we're not hanging out. That would only be acceptable if I knew you longer and we were already friends as bland conversation. What pisses me off more is most of these creeps have a SO. These are just people I'm just trying to reconnect with that I know from highschool, so rule out the internet-mojo vale. I can actually SEE these people around. Many of them have kids, yet here we are, flirting with people you barely remember. Out of 8 people I've talked to only 3 haven't done this. Wow really? You can't think of a conversation at a certain point that isn't about how pretty someone is? You're in your 20s, so you should have (and know) more things to say than a 13 year old boy.