Why are there so many extremely popular Vanilla TTT servers?

There are alot of Vanilla TTT servers that get TONS of players, I joined 10 TTT servers today and they were pretty much identical. I don’t get why because none of them are unique.

I know some possible reasons

-Good Staff
-No/Less RDM
-Good Community

What are some other reasons why? Just curious :P.

The server may have tons of nice regulars that are easy to get along with. Plus, good admins that actually take care of RDM’s.

A ton of servers with custom content are poorly configured and buggy as hell. Vanilla is a nice break.

Also a lot of servers have donator perks with OP guns or pay to get admin.