Originally Posted by
MistakeNot
^ This.
Adding servers is easy, but I think SE is very reluctant to do so until they are sure new servers are needed and will be needed long-term.
If the population shrinks, they don't want to be stuck with empty or dead servers. Closing or merging servers is not easy - especially not with housing working the way it does.
Some sort of mega-server technology where people appear to all play on a single server even when it is multiple servers underneath would be nice, but adding that to a game retroactively is a HUGE job, with plenty of potential for introducing new bugs.