Point is how many survive and how many die?
Most of the 'newer to the field' that come along go on the principal that all clients will not use it.
Unfortunately disk space kills that scenario as they can fill it easy even if no-one wants to download it, backups, files of all sorts.....
Usually you find server load is never considered, budget celeron and cramming 500 clients on it is a sure way to see you off quickly.
The 'kiddy host' sector gets hammered for this and it is the irresponsible ones that hide behind that, that cause this dislike for the previously mentioned. Not all but many do just spend birthday money on a cheap server and think they can host, and make a fortune. Wake up call - few of us make a fortune, and only after hard work and a lot of cash input.
Then some suffer and they're running very close and unable to cope so have to actually 'spend' some money' to keep it going and disappear. Sometimes having a years worth (or worse those one time payment hosts) of the clients cash in their pocket.
Responsibly done it can be managed if you have the finance to back it up but it does require carefull calculation. Not 100Gb disk space and 2000Gb transfer for $2.99 that's just stupidity kicking in without reason for appeal.
The big guys have cash to throw around and have various 'benifits' if they have to invest more - so they won't suffer.