Because ultimately, Israel only has four options. They can figure out a two-state solution. They can becomes an Apartheid Theocracy. They can become an Arab dominated Democracy. Or they can commit genocide on a scale comparable to the Holocaust.
None of these options are ones that are exactly wonderful. Israel will probably avoid the third option at all costs. And I would goddamn hope that even the US wouldn't support option 4 (Who am I kidding though, the US would likely cheer it on right now).