Apple is a fad that got propped up by phones. They're behind all other major computer vendors. They have a very small marketshare for phones. They have the biggest profit margin out of anyone, and it's because of literally a couple of products.
People who go for things with a huge profit margin (overpriced things) do so based on emotional response (a fad) as opposed to logical reasoning. This is why they buy a phone wrapped in glass - it's shiny. That makes them liking your product volatile. A company enjoying 15 minutes of fame on limited SKUs is not a successful company. It's a rich company, that won the lottery from people who like shiny things.
Yes, they do make things that "just work" better than the competition. They limit choice, put you behind a wall, give you no control - and there is that group of people who want that. The problem is, that group will overnight change to some new fad phone vendor that comes out, and apple will become uncool overnight. Same thing will happen to facebook, instagram, twitter, etc.
If you do take microsoft or google for example - they have a thousand eggs in a hundred baskets. This is stability. Heck, even amazon - cloud services and selling goods, book store, mechanical turk - they're in everything. Apple is selling a phone and a computer.