Anti-competitive behavior doesn't require a monopoly. There's collusion/price fixing, libel, and other ways to interfere in a business which are all illegal without having a monopoly.

If we use cars as an analogy, we require car manufacturers to allow service by other mechanics, but we don't require the same for phones (yet). Car manufacturers do not have monopolies.

At some point, asking, "Does Apple have a monopoly?" becomes the wrong question to ask.