Rather than the sex being about pleasuring someone else, it becomes about pleasuring yourself. Because you don't know the other person and you aren't talking to them, they become little more than a sex toy. People I've talked to about anonymous sex often talk about a sense of emptiness afterwards. Sometimes they've gotten so horny that they've had sex with people who they'd never have looked at normally, or they've done things that weren't within their safe-sex limits because they got carried away and didn't know how to take control of the situation to say what they wanted. Everyone's out to get the best partner they can possibly get.
Rejections can be brutal and ego-crushing.
The most successful tend not to be the best-looking guys but those who can force their attentions on someone else, not caring if the answer is no. A friend told me about a visit to a sauna where an older guy kept pestering him. My friend wasn't interested and kept moving away, but everywhere he went, this guy kept following him and touching him. If the end my friend had to physically lift the guy's hand off his leg. I have another friend who's calculated that he's spent a year of his life cottaging.