Slimrider's Youtube link in his post above is a bit puzzling: what, exactly, does subjecting frames to cutting with a circular saw, denting by dropping weights, etc., have to do with frame durability on the road? (Answer: nothing.) Slim, look up the German Tour tests I referred to earlier; I think you'll be interested and maybe even enlightened.
Maybe you have seen more failed aluminum frames than failed steel frames: anything's possible. I sometimes go for six months without a flat and then get five flats in two weeks. That's what we call a statistical cluster. I worked in bike stores as a service manager for about 20 years up to the late '90s, so I saw a very large number of bikes coming in for service over those years, and I assure you that I saw far more failed steel frames than failed aluminum frames.
But your experience and my experience are insignificant compared to that of the warranty claim processors at Trek and other bike companies. As I said earlier, the reported rate of frame failure for aluminum frames is lower than the rate associated with steel frames. Aside from the obvious weight advantage, that's why I've gradually replaced all of my steel frames with aluminum frames.