Oh, the chains themselves can fail, in a quite a dramatic fashion, flying through your engine hood.. But that tends to happen well after the mileage they were designed for.

They are by no means immortal, but, by design, should have a much longer lifespan than belts.

> Virtually every engine I know with a chain ends up either regularly failing early [..]

But I have no idea which early-failing models OP is referring to, as the engines I know about where quite reliable. (As in 1e6+ km reliable, with chain maintenance per manufacturer guidelines.)