Because these fuckers don't realize that THEY are the problem, their customs and habits, their way of thinking, their attitude, their nature, their personality. Some may realize it but think that they can be carried by white man's society, they won't collapse the system, they are just one little leech on a very big animal.
But now there are millions of and millions of leeches and the animal gets smaller and weaker, so soon there will be nothing left. But until then, they'll keep coming to try to get one more little drop of blood out of it.
Of course that's stupid and short-sighted, but that's how they are.