Enter the mind of the most common American male. Now you're in his head as he's being put in a room. And now there's a party going on in this room. And now there's two girls are only with one or two other people...looking a little bored or lost. One girl is pretty attractive...what he would consider an 8 or 9. The other is what he would consider maybe a 5 or 6 if he were being generous. Now, it should be noted, the common American male isn't that confident and also hates being rejected. So who does he walk up to and who will more likely be receptive to him if he does?
Many guys will go after the unattractive girl...why? Because they fear they won't be accepted by the hot girl. It doesn't make sense...a hot girl liking him right off the bat. The fear of going for it and it not working out is so paralyzing because he wants it so bad, whereas the average girl...it's whatever.
Here's another thing--he mistakenly believes the average girl will feel lucky to be hit on by him. He thinks in some twisted way that she will be like "omg a hot guy talked to me!" He thinks it's a layup and he thinks the attractive girl is a half court shot...oh the irony.
Average homegirl thinks you're patronizing her, or maybe making fun of her, or maybe just talking to her for a quick lay because you couldn't possibly be taking a girl like her seriously.
You're in the room now and, if you're lucky, she's only blowing off the common American male who's chosen to talk to her over the very pretty girl (by most classic standards) if you're not lucky she's literally verbalizing that she knows "what you're doing" and not having any of it and then you sort of shirk away to get another drink hoping no one saw that crash and burn and wondering what the hell is her problem. Why does this happen so often with the average ones? They believe they're average even more than you do and so it's classic rejecting you before she gets rejected syndrom. We as humans have strong held beliefs that we hold as facts. It's scary to think you could be serious and it's easier to dismiss it even if she came to the party for the single purpose of meeting an attractive guy.
So common American Male--don't put average girls on a pedestal as nicer than pretty girls. Yes, pretty girls tend to be more flighty because of their huge amount of options but they also tend to be nicer (in my experience.)
***This take is based highly on empirical evidence and in no way stands as a conclusive fact or definition about what to expect from average vs. pretty girls. This is what i believe most men will encounter in general, but of course there are insecure pretty girls and very confident average girls but they are not the majority. Also pretty vs average is obviously a subjective term...i don't like using the word ugly so i use the word average...