One of the leaders of the protest. Munir Abu, said that UNRWA's services to the Palestinian Arabs for the past six decades were not a favor, but a "right" of the "refugees." He claims that this right was affirmed by UN resolution 194 and lots of others, saying that until the Palestinian Arabs "return" to the nonexistent homes of their ancestors it is the international community's obligation to support them. He called on UNRWA to actually increase services, warning that failure to do so would constitute a "humanitarian crisis."
Nusseirat is in Gaza. It is in Palestinian Arab occupied territory. There is no reason the residents there should be considered refugees, even under the tortured UNRWA definition allowing descendants to inherit that designation forever, because they are already in what they consider their own land. There is nothing stopping the PA from dismantling the camps in its own territory and telling everyone to stop whining and do something productive.
But the reality is that the camps are there for a reason - to foment hate towards Israel, either directly via the residents or indirectly via people being angry that poor "refugees" are stuck in camps ostensibly because of Israel.
UNRWA has no plans to mainstream "refugees" into having normal lives - even if they live in "historic Palestine!" Rather than act like a real refugee agency where the goal is to reduce the number of people getting services, UNRWA encourages the problem to grow, and thereby keeping themselves in business to beg for more money every year to forestall yet another budget crisis directly due to their policies.
And so it goes.
(Update: Corrected a basic fact h/t Ian.)