Its been on the books since the 90's, but it would cost too much just to repaint lead painted homes, so nothing much has gotten done. Highlights of the program: https://www.cdc.gov/nceh/lead/about/2000s.html
This seems like a lame excuse. Surely the USA can up their water plumbing requirements without replacing lead-based paint on other surfaces. Other nations have regulated this for decades now. It's about progress, not perfection.
In the US, lead pipes in new construction were banned almost 40 years ago. This is not a matter of the pipes not being regulated, it's an issue of replacing older pipes.
I also think it’s one of those , “if we just wait long enough the problem fixes itself” type of things. That said, the question becomes, how long does a lead pipe work without failing? I suspect that amount of time is longer than anyone wants to admit. Apparently we’d rather give the externalized cost to prisons instead of plumbers.