It is just that only a rather small percentage of a MMO's playerbase is interested in PvP. With a small playerbase it gets rather hard to have a lot of people in the queues.
True. Once again, I must say that a 1v1 queue with some time-limited objective, or reducing team size in general (to 3, for example) would help PvP. The experience would be less random, and the waiting times would be shorter.
The problem is that we have a self fullfilling prophecy here. Without proper rewards, advertisement, new content, bug eliminating PvP will decline. With declining usage of PvP content Cryptic can't justify spending money on it ...
I think there is a middle way: It is not "all or nothing". Doing a few little things, like fixing Ker'rat (or only parts of it), adding a new PvP game mode or two every season should not require too much work. It doesn't have to be much to keep PvPers hooked.