I developed a very serious mobile app back way in the mid-90s for public health and disease surveillance. Let me tell you from experience why an app that people rely upon every day for critical work is no way to strike it rich. People *need* a lot of support for that kind of app. Support equals labor, and labor is expensive. Businesses with high expenses don't get rich unless they can command huge prices.
When smartphones came along, my partner used to gnash his teeth at stories of developers scoring windfalls with ringtones or stupid little games, and here we were doing *important* work and only making an OK living. I pointed out that if somebody pays $1.99 for something to amuse himself, he's never going to call tech support. When something represents a total investment of fifty to a hundred thousand dollars in hardware, software and system integration services, he damn well is going to call tech support. But 50K isn't really that much money if you include hardware, third party software licenses, QC'ing the client's existing data and converting it, training the administrators and end uses, and negotiating with IT gatekeepers. That's what you have to face when you do work that everyone agrees is important. Yes, people are willing to spend real money on important problems, but they also subject you to higher standards, intense scrutiny, and exacting ongoing demands, and those things eat into your profits. And the only way to get rich in business is to generate profits -- and salary you pay yourself for your labor IS AN EXPENSE.
That's why the $1.99 app somebody buys on a whim to amuse himself is bound to be more profitable than *important* software that somebody relies on to do something important -- no matter how much you charge for that software. There are exceptions to this rule, of course. Software that is a cheaper, more convenient alternative to something someone already has (e.g. Skype) is practical because what it does may be important, but that software itself is at first dispensable.
Look at the vast amounts of cash going into develop "social media"; it is no accident that most of it goes to support is so trivia. Trivia is profitable. It's easier to try radical new things in the trivial. A lot more people have an early adopter stance towards a service like Facebook than they do to towards things they regard as critical. They take convincing and hand-holding. That's why something like Google Wave couldn't get off the ground, you have to approach something as important as collaboration much more conservatively, usually working around how people already do things (e.g. Sharepoint).