So Apple's ecosystem does two things:
1. it gatekeeps what's in the App Store. This is of course controversial but is a net positive for consumers (IMHO); and
2. It provides a convenient payments infrastructure.
I certainly hope no government forces Apple to allow third-party App stores. Just look at what a mess this is on the PC where there are a million launchers (eg Steam, Epic, Ubisoft, Rockstar) and nearly all of them are terrible.
(2) also has value, even for big companies. There are definitely people who buy things (including subscriptions) on Apple devices because of the ease of doing so. Remember that cut also does include credit card processing fees so that sets the floor at 1-2% not 0%. That's still a lot less than 30% of course. And I think this is particularly egregious for recurring charges like Spotify in this case.
This is why I was utterly confused by Apple's move last year to lower the cut for small developers only. This is the complete reverse of what they should do. It's clear that the winds are blowing towards government intervention here so Apple should be looking to control the narrative and deciding what compromise looks like.
If Apple had come out and said that if you process more than $10m/year then their cut was 10% of initial purchases and 5% of recurring charges do you honestly think that Spotify or Epic or anyone else would be suing them or seeking government intervention to anywhere the same degree?
Apple (and Google) are just holding on too tight to the 30% cut and they're not reading the (antitrust) room.