Was it just a matter of convenience or a lack of suitable alternatives? Were the dangers really well understood or was there a dissent about how dangerous it was? I understand that it was apparently not used in large scale piping but only in smaller pipes inside a household or such but I still wonder about that.
And related to that: How much further back than Vitruvius can we go to see if lead was considered dangerous? Was it known in the Classical Greek era? In the Hellenistic Era? How about knowledge and usage outside of europe and the mediterranean?
On the one hand, yes, lead is legitimately dangerous, as science has proven. On the other hand, you're overestimating the danger inherent in the use of lead piping. On the Roman side of things, here's a few previous posts:
Given that the Medievals did use lead pipes in their own turn building aqueducts, one wonders if the lack of ruminations over the Medievals and lead poisoning is pop-cultural blindness (and thus too occupied with the Water Thing), a legitimate hole in the scholarship, or just me not looking hard enough.