First: a time / value mismatch; students don't want to spend more time doing something, then waiting before they get feedback, and your PhD students are taking longer to crit, annotate, explain their reasoning etc. through an interface than they would take vocally. In fact, a paid telephonic [ VOIPic? - Ed. ] mentorship service would probably do better.
Second: you didn't understand the market, not just your customers. The market is _everyone_ you have to deal with, not just those that buy the bread.
Third: I'd place PG's #5 (Obstinacy) covers both your 'knowing how to code' problem, and the fixated / obliviousness.
Knowing how to do something is just knowledge. Knowing why, when, and when not to is wisdom. In the end, it sounds like you're glad that you could afford the lessons.
Second: you didn't understand the market, not just your customers. The market is _everyone_ you have to deal with, not just those that buy the bread.
Third: I'd place PG's #5 (Obstinacy) covers both your 'knowing how to code' problem, and the fixated / obliviousness.
Knowing how to do something is just knowledge. Knowing why, when, and when not to is wisdom. In the end, it sounds like you're glad that you could afford the lessons.