While Apple does not have a monopoly over the smartphone market by any meaningful definition, what it does have is a vastly outsized mindshare.

Not only did Apple invent the modern smartphone, they created the first modern App Store. This, combined with their high cultural cachet, allows them to define by their actions what an App Store "should be" in many people's minds.

Personally, as a lifelong Apple user, I'm both concerned about Apple's singular control over the iPhone app market, and concerned what would happen if that singular control were broken.