Contributors are there to earn points and just try whatever answer comes to their mind even if it's so vague or approximate that it is useless. Just trying, nothing to loose.
I guess the experts went away from it because the initial thrill has gone (sign of smartness) and they have better things to do then stare at a browser to catch new questions for no other rewards then getting points.
My impression is that stackoverflow was initially in a virtuous circle and now it's in a vicious circle.
I now have questions like how EXT4 files with holes impacts performance of an mmap ? Should I force a prior full fill of the file with dd before mmap ? I'll certainly get crap answers and I really don't know where to ask this to get a valuable answer. So I'll end up doing a benchmark, which has probably already been done many time or people knowing how EXT4 works could answer straight out of the book.