Maybe nowadays Bitcoin campaigns are coming up more often but don't forget that this campaign is running for very long time and if I am not wrong since from 2014 so some people love to stick with the long term campaigns instead of moving to campaigns every week just because they get few more pennies.
Plus, when you consider if you are a big name there, like get listed at A list, then not get paid for 10 weeks so you get a big bonus, it does become like any other payment. Definitely other places pay a lot more weekly, and you are required to spend a lot of time here (maybe shorter here since people at high levels may leave for one that pays weekly) then you get to become a high tier participant who gets big bonuses time to time when the payment is done.
I haven't checked but if we checked the highest paid person on the last payment, I am sure when you calculate the weekly, it is closer to the ones from other campaigns as well. So there is "some" reason to stay here, not really logical but at least reasonable.