I don't think the people who work on these "useless" apps are to blame, rather it's the system in which they are brought up in and in case of start-ups, are taught entrepreneurship in. Paul Graham himself says he advises every start-up to "work on something for which they are the initial market"[0], so every YC cycle you get numerous companies which solve the problems of young San Francisco residents ([1] for comic relief), who help you save 30 minutes of your week you can then reinvest into working more on problems which aren't really problems while the world crumbles around you, but you don't really care about that because your Uber driver doesn't drive through those neighbourhoods.

Meanwhile, your doctor in the hospital is stuck using some 1980's software, which drains the very life-force out of him by the amount of pain it inflicts with every use, but you'll never need a doctor anyway, not with this healthy-eating/exercising app, plus it's too hard to work on that with the regulations and all, and the carpeting in your apartment is moldy.

[0] https://news.ycombinator.com/item?id=6106528

[1] http://www.youtube.com/watch?v=guf0kNV7D1w

ps. On an honest note, I've been working both on apps of the "useless" type, and spend most of my time on working on "useful" medical apps, and fuck if it's not easy to see why no one thinks these areas "sexy", so bogged down in regulation and old entrenched players. But I still think, at least in the case of these super incubators, who have the connections, who have the access to the financing, the focus should be on something more than what it is right now.