Earlier quoted context omitted.
I know you know the answer to this (i.e. move to another vendor, as you would for any vendor that goes away), so my apologies in advance for not understanding the point you're trying to lead me to. I guess I don't understand the alternative. Go out of business?
I think the choice is between using a solid platform like the App Store or something like it, or building your own using tools that won't go away either. Stripe, PayPal, things like that. It takes a lot of effort to build out your own store and get it right, this is no small task, which is why the 30% fee charged by these stores is not necessarily the biggest obstacle. These intermediaries add considerable risk.
Edit: Sorry I know those were just two examples - I'm not trying to refute your point