You're assuming they actually believe what they're saying. I'm sure some of them do but for others it's just another way of bragging. They're so good they don't even realize what they're doing is hard, don't you see?
Don't get me wrong, there are times when I would probably do the same thing. Let's say Meghan Fox walks out of my bedroom and passes through a by a few of my friends on her way out the door. When they finally pick their jaws up off the floor and start grilling me for answers am I going to say "OMG I still can't believe it either!!!"? No, of course not, I'm going to say "Oh, Meg? Yeah she's a cool chick. So what are y'all up to tonight?" However it's a stupid thing to do on the internet, a rude thing to do to a stranger, and an incredibly rude thing to do to a stranger looking for help.