tl;dr Apple = closed. BTC = open.
To be honest this thread and your theory will come sooner or later, because as you can see the bitcoin gaining more popularity than last year , and I think that apple will cooperate with bitcoin as a paying. Because bitcoin is still not illegal on some country so I think this is why apple still not accepting the bitcoin.
Their competitors do plenty of things that Apple doesn't, like open the platform for development for example. That's far more consequential than something dumb like accepting crypto. Apple isn't going to do anything that doesn't benefit Apple, and if you think getting involved in crypto to please a fringe minority matters to a company worth $850 billion, you're just wrong. Wishful, but wrong.
As a leading brand and company, Apple won't likely decide to accept cryptos unless they see it as an opportunity for them to generate more sales. Only a number of their consumers would be assumed to be using cryptocurrencies and it can't be said that it would be a benefit for them if Apple were to accept it. Apple should work on other features otherwise they may be left out. Other brands already have better features and if they don't improve, they Apple may lose their loyal customers.