I'm sure that's no accident. I suspect they're at the empirically determined sweet spot between 'beautiful/sexy' and 'loose/easy' for the maximum number of people to feel they'd both stand a chance with the person and actually would want to have sex with them.
I actually got one of these requests and reported it as a scam. One of the reasons I knew it was a scam was because the facebook picture came from one of the stockphoto websites.