The thing is that at least temporarily and at least in certain niche markets they come close to being a monopoly. There is no credible competitor to the Ipad in the tablet market. In the smartphone arena, the Iphone is a run away success with more marketshare than any other by far.

Also, remember there are a lot of people that want a walled garden. It makes them feel safe and shields them from needing to really understand any of the details. I am certainly not one of those people, but that market segment will exist even as new tablets come out and the competing smartphones gain marketshare.