If so they already have 22 countries. The West Bank and Gaza were controlled by Arabs but not Palestinians, rather Egypt and Jordan. If so why didn't the Palestinians (and the world) demand an independent Palestinian state in the West Bank and Gaza from 1948-1967 instead of Jordanian and Egyptian rule? The fact is that no one suggested establishing a separate Palestinian state because there never has been one and there never was a separate Palestinian identity until the 1970's.
Regarding your second point, all of the Arab countries came into existence based on that same conference.