> It's hard to imagine why the U.S. ever had a single lead water pipe, let alone huge numbers of them.

Lead has some advantages. Its melting point is low, so it's easy to weld. It doesn't corrode quickly, so pipes last a long time. And it's malleable, so pipes don't break when soil and foundation shift. But yes, it's very poisonous, so the advantages are moot for drinking water.

For corrosive waste plumbing, on the other hand, it can be a good choice. It even tolerates HF, which glass doesn't. Glass is sexier, however.