Then why don't don't all aluminum pistons have bronze bushing inserts? Or aluminum connecting rod pin bores? Or main and rod bearings for that matter? That is why I question it.
Pistons are not a bearing fit tolerance in the cylinder bore, the rings are in hard contact. Can't answer the others, I've seen some that do and some that don't. I would put bronze in anything that wasn't getting regular tear down and inspection. I'm sure there are coatings that help too. It probably comes down to cost and required durability in most cases.
