"I read articles about giving some random homeless guy money and programming training, and then he has an app in the app store for iPhones. Why don't we just do that for all of the poor people out there? Everyone can write their own app, get training and support, and get some startup funding and see if it works out they can have their own small business. If not, well at least you tried."
Because it makes the already super competitive field of app writing artificially even more super competitive, and probably doesn't add as much good to the world as the same people could elsewhere, and probably doesn't actually make these people enough money to do much (plausibly not even survive, absent other supports).
Well, we can train for something we know there is excess demand for, but that involves picking winners, and the people who are great at that don't usually work in government bureaucracy (and only occasionally work in charity).
Another approach is to ask people in less need of paid work to make room - a low Basic Income has that effect: as some people leave the workforce to focus on unpaid activities (child rearing, volunteering, art, educating themselves), this leaves more jobs available for those who need them.
Because it makes the already super competitive field of app writing artificially even more super competitive, and probably doesn't add as much good to the world as the same people could elsewhere, and probably doesn't actually make these people enough money to do much (plausibly not even survive, absent other supports).