I live in Europe. And for me interested which material use in other parts of world for plumbing. For example in new build houses for both types water used plastic pipe. but for heat used cooper pipe. which material used in your region?
In US, I live in Illinois, the state we install water pipe thats pex, cpvc, and copper. For drainage, we use PVC, but in the city of Chicago the drainage is cast iron.
Mostly political reasons haha, the plumbers union has done a lot of work to keep cast iron in the code, because it means the people doing it have to be skilled plumbers. There are other benefits of it though, like if a building catches fire, plastic will melt and the fire could easily spread to other floors through the holes while cast iron would block it.