To be fair, in the US we did ban admission of polygraph evidence in court, but that’s just the tip of the iceberg in terms of problems they and other psuedoscientofic “investigation” techniques create.
I think that while a lot of reasonable people know that lie detectors are bunk, a surprisingly large number of people don’t know that at all - and many of the people who seemingly know better still haven’t actually confronted what that knowledge means. Like if you say to someone, “I took a lie detector test”, it lends credibility to what you’re saying for a lot of people even though it shouldn’t lend any at all.
Take this out to the whole world of phony pauedoscientific criminal investigation techniques, and the number of people in a world poisoned by shows like CSI who would rightly support banning such things is going to be shockingly low, even though everyone with knowledge on the subject can probably tell you that’s what should happen.
So that’s why there’s no public pressure to do it really. Add to that the fact that law enforcement doesn’t want their psuedoscience taken away from them because they see it as a useful tool in getting convictions, and any politician who tries to take this issue on is going to be acting alone against entrenched power for basically no political gain.