Services. There are currently 1.3 billion iOS devices on the planet, being used. And even if that number only grows at a few percent per year, that’s more than enough to grow a huge services/streaming/news/books revenue. Apple is tech reliability, and tech trust. I can buy my computers, phones, watches, tablets, speakers from them far less often than with competitors, and I don’t have to give them my digital existence to make use of Apple’s technology.