Crashes and Fires

I've noticed that a lot of crashes, in particular with light aircraft, don't result in post crash fires. Just this week I've seen a couple of accident photos involving recent crashes of light aircraft, one into a house which didn't take any lives, where there were no fires. I imagine a crash being horrific enough without having to bail out of a burning airplane. It's not like you can just put it in park and step out. I've often wondered about statistics on such a subject. Just how many crashes result in burned out aircraft corpses?

Since getting into ATC, I've watched many incidents and accidents from the sidelines and very few fires have taken place. Most lives were lost to g-forces and/or structural damage or injuries on impact. And yet many airliners end up burning after a crash. I wonder if it has something to do with the amount of fuel on board, the speeds which airliners carry over light singles, maybe a combination of both? The extra energy that must be dissipated in a crash from a higher speed may result in more heat or sparks to ignite the contents of ruptured fuel tanks. Obviously I'm not an accident investigator, though that field has always interested me.