Why did Egypt immediately close their border as soon as Israel granted the Palestinians their own Jew free Gaza? That wasn't very nice. Especially since Egypt had an open border with Israel. What could have prompted such behavior among the Egyptians against their own peace loving, life loving Palestinian brothers?
US Annual Aid to the Palestinians is a huge number. The Palestinians receive international welfare payments from the UN (UNRWA--mostly funded by the US--annual budget ~0.5 billion), the European Union, and (inconsistently) fellow Arab nations. The Hamas-Fatah split has complicated this, but total annual contributions are estimated @ 1.5 billion.
http://www.usaid.gov/locations/middle_east/countries/wbgaza/
That welfare money would dry up if Syria, Egypt and Jordan allowed the palestinians back into their homelands. There is simply no chance that Syria, Egypt and Jordan are going to accept financial responsibility for Pal/Arabs
not when a dedicated UN welfare agency will do that.