The answer is likely that the treatment is expensive, and most people aren't drinking tap water anyway.

My town completed it's pfas filtering system and water bill costs increased about 25% to cover it. I don't know one person in this town though who doesn't drink filtered water.

That being said, I do still support the filtering.

Is this a regional thing? AFAIK everywhere I’ve lived most people drink tap water. Certainly they cook or make coffee/tea with it. But I’ve been lucky enough to live in places with pretty good tap water.

This is the reason. My city is struggling to fix its water supply that was broken over a decade ago (our water supply comes from a temporary system) since FEMA sent our funds to other things under the first trump admin.

They don't want to put the cost on the consumer, but there is no other choice. If our government was smart (it's not) they would make these rules and fund the changes.

Most people low and middle class people I have met my whole life drink unfiltered tap water unless there is a reason not to (safety or particularly foul taste). you might be in a bit of bubble. Not that it matter though as most bottled water is just bottled tap water anyway.

I never drink tap water. I cook with it, though, and would still very much like for that to be filtered.