The Humiliating History of the TSA
theverge.com
theverge.com
I, and everyone I know who travels, asks this all the time. Other than the TSA being an employment scheme, I don't have an answer to that question.
This is a really common effect in government and even companies. If it's important to be seen as doing something, something will be done, even not very effectively. It is far better to be seen as genuinely trying but not quite succeeding than to not even have showed up.
I doubt the employment program aspect of it is relevant at all, except in the sense that once a program is created, it is hard to get rid of it.
You and I might very well be smart enough to see it's a waste, but there's over 300 million Americans, and a lot of them vote, and a lot of them don't have the habit of thinking that critically.
So that's what the TSA is there for.
PS: Out of curiosity, are you old enough to remember 9/11? I hypothesize not since I hypothesize it would be obvious to someone alive at the time why TSA exists despite being ineffective, but I may be wrong. Just curious. Making me feel old!
Hopefully one day TSA will be sunsetted, but as mentioned, it's a jobs program now.