because during the early Roman republic food was served on Pewter plates, occasionally simple lead.

I'm embarrassed at how long it took me to realize why there was so much lead in the Roman world. It turns out that most of the world's silver is found as a very small (e.g. 0.5%) component of galena, which is lead sulfide. So silver mining, which the Romans did to pay for their empire, was producing literally tons of lead that were essentially a waste by-product. There are of course exceptions. The Bolivian silver mines near Potosi are not a lead ore and this is why the Spaniards caused the silver market to crash when they opened that mine. And curiously there are lead deposits that are not silver-bearing. Geo-chemistry is complicated. One can monitor the silver mining output of the Roman empire by looking at Pb concentrations in glacial ice in Tibet.

Anywho, lead was, in addition to being easy to work due to its low melting point, really really cheap. And lead pipes will develop a pretty decent protective oxide so the amount of lead leaching into the water pipes isn't that much. Unless you change your water source and the new water chemistry is different (cf Flint, MI).

Rgds,
HH/Sean