I feel like more people would join if more information on the war was given. I mean, I would certainly help Good out since they look short a few players, but I also wouldn't want to hinder my team by not having upped cards of that element. I've only played for about two and a half weeks, and I've only worked on my Rainbow deck (fully upgraded) and upped 40 other cards.
If Water needs some help though, I'll be glad to help I guess.