I totally get the "their store, their rules" take, but it doesn't hold up in this case. Unlike most retail, there is no other store to go to. Sure, I could buy an Android phone, but the policy isn't much different there. The fact of the matter is that Apple & Google own the mobile ecosystem.
It is one thing to claim that the your marketplace is doing developers a service by distributing and putting their apps in front of their massive audience. Fine - collect 30% for downloads/subscriptions that come that way. Unfortunately, there is effectively no other way to consume software on these devices. Keep your 30% of downloads/subscriptions that originate from your marketplace, but let me opt-out of your marketplace and still get my product to my customers without your help.
It is one thing to claim that the your marketplace is doing developers a service by distributing and putting their apps in front of their massive audience. Fine - collect 30% for downloads/subscriptions that come that way. Unfortunately, there is effectively no other way to consume software on these devices. Keep your 30% of downloads/subscriptions that originate from your marketplace, but let me opt-out of your marketplace and still get my product to my customers without your help.