I don't know about EU1,
but I guess the main reason why there are so few people playing in all actually is that EU7 gives too easy, too high reward, as Saxon said, full server... all the day. Even old DTV players want it to be decreased, me too.
Also, the few times I played on EU2 now again, I realized Conquest comes up a bit too much, and mostly leads to the fact that many people quit - I'm not sure tho.