Just because a girl posts on the SNATCH doesn't make her hard up for customers. It's the easiest way to let everyone know she's playing today.
Now regarding pics, I've had many men send pics unrequested. I don't pay it any mind myself but it is nice to put a face to a name since we are mostly going in blind.
Also, it is really up to the girl who she wants to see or not. And she doesn't "owe" anyone an explanation for her choice. Yes, she is getting paid but it is ultimately her body and her choice. She's more at risk than a man in my opinion so if she doesn't feel comfortable seeing Joe Blow because he's a big guy or Bob Dole because he is annoying her with his PMs, THAT'S HER PREROGATIVE.
Personally, I like the fluffier types myself, they're fun to bounce on.
But a fit guy is fun in other ways.