Because that's not actually the case? Only a small part of the FAA's activities is post hoc incident analysis. They do quite a bit of scientific studies, certification, licensing etc. And in fact the most recent outrage against the FAA has been the feeling that they have bene derelict in their duties in regards to the 737-MAX by adopting the problematic self-regulatory approach used by, say, the Department of Agriculture.
By contrast, the TSA (which is much smaller than the FAA and has, for all intents and purposes, only one responsibility) on has never demonstrated competency, clearly awards contracts based on cronyism (the millimeter wave system have no science supporting them), engage in absurd scope creep (checking bags on some train or bus stations, pretending to be law enforcement) and reducing security from where it was before the agency was created (e.g. "TSA locks" which have permitted an increase in theft from bags) etc.
Not at all the same.
Source: https://abcnews.go.com/ABCNews/exclusive-undercover-dhs-test...
It appears that most people on HN feel that TSA regulations are pointless theater and should be weakened or eliminated, while the FAA is to be blamed for not exercising their regulatory power strongly enough (especially in light of the 737 MAX).
Both agencies seem to follow a similar methodology: when there's an incident, analyze the cause and enact regulations that would have prevented it, building up a system leads to fewer incidents over time. And they seem to have led to similar results -- over the past decade, there has been only one passenger fatality on commercial flights within the US due to accidents, and zero due to hijackings/bombings.
Why the difference in opinion? Is it that TSA regulations are personally annoying to travelers while FAA regulations are mostly invisible to passengers?