But Mac sales pale in comparison to iPhone, and are similar to iPad numbers. So whatever revenue they would lose by not selling Macs with macOS, they could easily make up from additional sales of iPhones and iPads with macOS.

Besides, they've increasingly been expanding iPadOS to have more desktop-like features, so it wouldn't be far-fetched to offer full-blown macOS on these devices. It's not a hardware issue at all at this point.

Why would they spend a bunch of money to trade sales of one of their products for another?