So the supposition here is that the "perfect vehicle" would be a subcompact, and that this one size of vehicle would best suit every drivers individual needs.
Huh. I would disagree.. wholeheartedly. I don't drive a subcompact, never have. Might have a lot to do with the fact that I'm a pretty big guy, I don't fit well in most subcompact cars. Might also have something to do with the fact that my requirements for a car are not "the smallest, most fuel efficient vehicle it's humanly possible to engineer".
Likewise different people have different tastes when it comes to cameras. For those of you guys who like small/compact.. great. Wonderful. More power to you. Try to take away my DSLR and replace it with something that doesn't fit in my big gorilla hands well? Nope. You'll have a serious fight on your hands.
I don't want small, compact, hard for me to use with my big paws. I don't mind carrying a big, bulky, 4 lb lens - doesn't bother me a bit, I actually prefer it.
So if a smaller camera works for you, and for this guy, great. Happy for both of you. But it doesn't necessarily follow that a smaller camera is the best choice for everybody.
Same reason they still make SUV's, BTW.