In particular, by the time a problem becomes prominent enough to be noticed by politicians, it has often already been solved and the ensuing legislation is nothing but a deadweight loss.
For example, before 9/11 the assumption was that hijackers would try to ransom the passengers for money, so it was better not to resist so they didn't hurt anybody. After 9/11, the assumption had to be that they were planning to crash the plane, at which point all the passengers resist and a hundred passengers can easily take on half a dozen hijackers and it's well worth the risk of one or two getting hurt in the process.
So by 9/12, another 9/11 was no longer possible. It was already solved. None of the government action that followed was actually necessary and the TSA is completely pointless.
Politicians generally don't understand this. Average people don't understand this. But it's still true.