quote:

Overweight:
Cuz the hot chicks tend to be able to get what they want without spending lots of time online or finding a sub culture connection...or rather, the hot chicks BELIEVE they can, the non hot chicks are generally insecure so they are less likely to have found security in their relationship, more likely to go online, thus more likely to find kink, and more likely to want to be part of something they've fantasized about and where they can be useful and valued beyond their body.

Older:
Because the majority of people still only get into kink AFTER they've done the typical life thing and after seeking online for some escape or other option.  Also, it takes money and leisure time to get into a sub culture, something youngsters don't have as much of.

White:
Related to the money and leisure time, minorities are less likely to have both of those, as well as whites lacking the social stigma of doing things alternative (white goth/emo/freaky kids is practically a cliche) and the higher security to not worry about being outed, AND the lack of historical stigma attached to these sorts of kinks and fantasies