Any politician who supports weakening surveillance or anti-terrorism measures will be out on their ass as soon as there's another attack (maybe sooner). And there's always another attack. Unless that's the only issue they care about they're not going to sacrifice the possibility of advancing other parts of their agenda to commit political suicide over it.

People are willing to revisit it but it ends up ending in one side of the debate yelling "BECAUSE TERRORISM!" and then plugging their ears as to not listen to a response.

Mind you, the "one side" isn't a particular political party, it's both, depending on the context that lead up to the discussion.