They aren't; they're motivated to ensure ice-cream machines are only fixable by them. Still a perverse incentive. It makes zero sense for a company to be motivated to have their own product... not... work.

Your last sentence goes a bit too far. There are products that are "loss leaders" that the company does not want to actually sell

A loss leader is working if it's increasing customer traffic. Nobody is going to McD's because they have amazing/cheap/highly-available ice cream.

I have definitely gone to McD specifically to get a shake on a hot day and driven away when told the ice cream machine was down.

the loss leader is the ice cream machine

The coffee is pretty good, though.