Some people hoards many Internet domain names.
It looks to fall in their personal tendency area. It may be his/her hobby, investment or peace of mind against future competition.
As a website developer, sometimes, I found some businessmen have many domains in many web hosting services, even though he is not in technological fields, and does not have a hobby of domain name collection, neither affords to keep them.
Actually the Internet domains do not need an exclusive web server. That is, it is typical that a single web server hosts many domains.
Some web hosting companies open the wide gate for a person with one domain / one server, however, while a narrow gate to who prefers many domains / one server.
I guess such gate policies are supposed to help web hosting companies survive in this tough business line.
As to consumers, frankly speaking, sustaining many web servers costs extra money and is a cumbersome job as well.
Some knowledge and tools would be enough for us to keep many websites in a single server. They are SSH (Secure Shell) like PuTTY and web server operating systems like Unix / Linux.
Whenever I asked web hosting companies for such open free tools, it took me several hours on multiple lines. After some guys take so long time to get understood my request, others open the gate in slow motion. LOL ~
It seems to be a cultural tradition.