I realize the very real risk of cross connections. That's something so serious and so cheaply remedied that I think municipal water depts. should just go around and install vacuum breakers on hose bibbs while taking meter readings. But even our Nanny state hasn't done that.
Our nearby capital city requires metal DWV. They're no safer than we are, but the union is happy. I suspect that's a big part of how Cook County got where it is regarding plumbing.
I've seen enough to be cynical about all politicians' actions, including the content of codes that get enacted. Some plumbers in our town think house traps are a good idea so that unused drains don't allow sewer gas into the houses (explanation from DPW). I guess that's to protect the home of snowbirds who go to Florida for 6 months and are too stupid to take measures. So, to be hooked up to the town sewers, you need to have a house trap. Prohibited, so I'm told, by some modern codes, but required by our sewer dept.