If I understand correctly from my neighbors’ experiences, they just cut up your walls and put new pipes in there and in the attic when the time comes that you inevitably develop a slab leak. it seems like this is probably a case where it has plenty of advantages for the first owner/1st 30 years (pipes neatly out of sight on the first floor) and when it eventually fails, it will be someone else’s problem besides the original builder or even original owner in most cases. Maybe this has changed in recent years though with the switch from copper to PEX, idk if they can just put that in the slab.

In New Zealand PVC pipes are used in concrete slabs for sewage, which in theory should last something like 75+ years. Water, I think, is still put in the dry wall cavity.

That's correct for water lines, and is expensive. But drain and sewer lines are in the slab. Just imagine the cost of removing your tile flooring, then cutting up the slab, removing the usually copper drain line (on older homes), laying new PVC, back filling with sand or gravel, THEN recovering the floors. Carpet would be a little cheaper.

Doesn't that just imply that a concrete home would have this problem everywhere, instead of just in the foundation?