Primarily because audio takes a fair amount of time and effort, and while money can buy lots of things, time is not for sale. It takes a fair amount of time to assemble a decent rig, collect a wide variety of music to enjoy, and more importantly the time to enjoy it. All of the accumulated "stuff" you listed is easy; buy and let it sit around or use it every now and then, perhaps pay someone to look after it, no real effort expended on their part. These people have things, but no real interests or passion in their lives.
Why Don't More People Love Audio?
Can anyone explain why high end audio seems to be forever stuck as a cottage industry? Why do my rich friends who absolutely have to have the BEST of everything and wouldn't be caught dead without expensive clothes, watch, car, home, furniture etc. settle for cheap mass produced components stuck away in a closet somewhere? I can hardly afford to go out to dinner, but I wouldn't dream of spending any less on audio or music.