Geek hobbyists
@ TheOtherHobbes - some of us prefer 4*5 or larger simply for the lens movements - and some of us build our own cameras... don't know if that counts as geekish or merely points out that we can't afford to splash a couple of grand on what is essentially a box with a bendy bit in the middle and a hole at each end!
I don't *care* whether or what others care about my photography; I don't do it for them.