That is my point. The features of the 7D may be useful, but I do not really need them to get good shots. But the 7D is considerably bigger and heavier. If they can make the 7D as small and light as the 550D, then I'd buy it. If they can make it even smaller and lighter, I'd pay even more for it.
I see this very often... my friends and family frequently have very fancy cameras. Just a couple of weeks back, we had a gathering with a couple of friends and their kids. A friend came by with his Nikon D300. Kids were running around and I could barely keep up... but this guy, was shooting single shots of the kids. It's like aim, focus, shoot... aim, focus, shoot. I was firing off at least 3 shots at a time. A person with his shooting style, does not need a camera with high fps. My point is... most people are not making use of the features of their excellent cameras... which makes it a real waste. OK, they have money and they can spend it whatever way they like... but do they know that they are lugging around unnecessary weight? I find the extra weight a real pain.
I have another theory... I think a lot of people buy the best cameras so that they can show them off to their friends. They are not making use of most of the features. For me, I upgrade my camera only when there is a real need. I just bought my 550D last week because the high ISO noise of the 450D was rather distracting. I am shooting ISO800 and 1600 a lot these days as my daughter is at the age where she runs around... and I really need to keep the shutter speed at 1/500. The noise level of my 450D was too high. The 550D with the excellent sensor is so much better.