"What problem does it solve" is typically the question asked to motivate conscious attempts at disruption using something like the lean startup methodology. Usually this means looking for a category of customers who are jury-rigging solutions to some incredibly painful real problem, and are hungry to buy any better solution.

This framing fits some designs better than others. It does not fit the App Store very well. The App Store is more of a vision-driven design (VDD) than a pain-point driven design (PDD).

Even if there was a class of people who were doing complicated things to get little software apps onto smartphones (I am sure there were -- jailbreakers etc.), the App Store didn't come into being to serve those in-pain (or more likely, "bored") jury-riggers. It came into being via a vision of serving a population who weren't in pain and weren't thinking about this problem at all.

Unless you consider blackberry users annoyed by the painful nature of getting new capabilities onto RIM devices. That is not a compelling case because the AppStore did not cannibalize a lot of RIM users. Instead, it got a lot more dumbphone users onto smartphones.