The real reason is not "the Palestinians are troublemakers".
The whole point of Palestinian refugees is that they create a permanent unsolvable crisis for Israel. If the refugees were allowed to leave Gaza and the West Bank, then Israel would no longer have a problem with periodic wars with the Palestinian refugees.
They also are useful idiot cannon fodder. Iran wants to go to war with Israel, but they don't share a border with Israel and open war is risky. Instead, they get to use Gaza/Hamas as proxy soldiers, providing arms and strategy smuggled into Gaza.
They also give massive foreign aid and encourage them to have max children. This further exacerbates the demographic problem. There were only 700k people displaced in 1948, and Israel probably could absorb 700k people if they had to. There now are 7M. Israel can't absorb that many people. If they were given the right to vote, Israel would have an Arab majority.
There also probably would be open civil war between Palestinians and Israel if they were allowed unlimited access to Israel. That's the whole reason the border wall was built in the first place, to prevent suicide bombings and terrorism.