That is due to the fact that there is in reality no such thing as a sub group of Arabs called Palestinians. Even Arafat who claimed to be Palestinians was born in Cairo of two Egyptian parents, served in the Egyptian Military, something that would have been impossible unless he was Egyptian, then suddenly in 1969 they all claim to have turned into Palestinians. I think one of Arafat's associates said it best:
Azmi Bashara was an Arab Member of the Israeli Knesset who fled Israel when charged with treason against the State. In 1994 he said "I think there is an Arab nation. I do not think there is a Palestinian nation. I think it''s a colonialist invention. When were they any Palestinians? Until the 19th Century, Palestine was the south of greater Syria."
Auni Bey Abdul Hadi who, in 1937, told the United Nations Peel Commission "There is no such country as Palestine. Palestine is a term the Zionists invented. Palestine is alien to us. Our land was, for hundreds of years, a part of Syria." So, there is the link between the Arabs of the 1930s and the Arabs as recently as 1994.
Walid Shoebatt, who was a former PLO terrorist, acknowledged the lie he had been fighting for when he asked, "Why is it that on June 4th, 1967, I went to bed as a Jordanian and woke up as a Palestinian? We considered ourselves Jordanian until the Jews returned to Jerusalem. Then, all of a sudden, we were Palestinians."
Even Yasser Arafat, the so-called founding father of the Palestinian cause, admitted in 1970 to Italian journalist, Arianna Palazzi, that "The question of borders doesn't interest us. Palestine is nothing but a drop in an enormous ocean. Our nation is the Arabic nation. The PLO is fighting Israel in the name of Pan-Arabism. What you call Jordan is nothing more than Palestine."