Because the wealthy Arabs like the Saudis and the folks in the UAE dont want the Muslim equivalent of riff-raff, mostly coming from North Africa and parts of the Mediterranean, living in their countries! Thats also why these countries never offer to take in Palestinians. Theyll use them to antagonize Israel, but keep them the hell away from their borders!
Ditto for the elite white Mexicans who don't want the mestizos living amongst them, so they want them to go to the US.