Because the LIEden MalAdministration is stuffed full of Israel haters. Both were invaded, neither should negotiate until all of their territory is liberated and the invaders have assumed field or sand temperature.
I think that's their "out". A significant chunk of Ukraine is still occupied, and a ceasefire presumably would not change that. But presumably, a ceasefire in Israel would mean the same borders that existed before.
That being said, a ceasefire now would be like someone punching you in the face and the. Saying "no more hitting". Israel has to takedown Hamas...if they can.