It isn't. There was an article in the Jerusalam Post a few days ago which provided an explanation.
The peoples of the surrounding states may not like Israel but they can go on with their lives. Palestinians are reminded on a daily basis, in the most direct and brutal ways, of what they've lost and how poorly they live...and there's very little they can do about it. Their "state" is to small and poor to provide them with opportunity.
Now, if the Arabs were truly one people the Arab part of the West Bank would be joined to Jordan while Gaza would become part of Egypt. I think that was the motivation behind Israel's withdrawal from Gaza. But it faces huge obstacles because Jordanians do NOT want more Palestinians and Egyptians aren't crazy about them either.
Even Europeans are finding it hard to give up tribe and nationality. Arab society and religion are medieval. For them it's impossible.
I think your position fails logically. Almost as many Palestinians, excluding fedayeen, live in Jordan as live elsewhere. And the West Bank WAS part of Jordan from '48-'67.
While there are ruling families/tribes, and jealousies between others, there exists no one tribe - one country rule in the Arab world.