We still used lead, and paper, to protect cables, like a 100 years ago

However, a lot of the polymer based insulation HV cables installed in the 70's and 80's have failed prematurely, most notably XLPE water treeing issues, which have cost many billions of dollars.

Installation costs often dwarf cable costs, especially in high density population areas.

There are also benefits like lead having better fault current tolerance and moisture resistance and many other technical details.

There is way, way more to cabling, and especially HV cabling, than most people realise. It isn't just run two wires from your AA battery to your torch bulb.

People make entire careers out of this sort of stuff and there are no easy answers.

We also still use lead in most car batteries, gun projectiles and fishing sinkers, not sure what your point is.

(PS : And for that matter, the use of depleted uranium in armour busting shells is just because of the availability and atomic weight, I am far more outraged about this.)