I have also seen those who have refused to move to campaigns with better rates, they will be picked if they applied because of their good posts. They choose to remain. Is it about loyalty? Is it that they are scared of switching? Is it about fulfilment with where they are?
You probably didn't have me in mind when writing the above, but I related to that particular situation more so than the others. Personally, I'm not on this forum to make money and I don't like switching campaigns frequently because I don't want to burn bridges; when you leave a campaign, the manager then has a slot to fill and it's more work for him. So although in the past I probably could have gotten into higher-paying campaigns, I chose to stay where I was for the reason I gave (and I don't want to get the reputation of being a campaign-hopper).
Everyone is different, though, and if you think about it, it's a good thing people are jumping to campaigns that pay more. That in theory should drive up pay rates across the board, because if you're renting signature space, to get good posters you need to pay a competitive rate....just like in the real world, you know?
This forum is basically about money and if people are honest most of them would identify as capitalists. And what do capitalists do in the labor market? They go where the money is. It's not that tough to figure out.
Oh, I think this thread ought to go in Meta or Service Discussion. It's an interesting topic to me, OP. Even the idea of sig campaigns has fascinated me ever since I figured out what they were (and that took months for my pea brain to compute).