They're regulated. The problem is that our threshold for bad monopolistic behavior is that customers suffer, and it can be damn hard to prove when it's indirect, like in this case - how much do customers suffer from not having access to the app in question? But even then, when you aggregate all that across the entire store, I'd say that there's that aspect as well.

Back when our anti-monopoly legislation was first introduced, that wasn't the case - monopolies were busted just as well because they did something anti-competitive, even if that was presented as benefiting their customers (and even if it really did, short term).

https://ir.lawnet.fordham.edu/flr/vol81/iss5/6/