The 'scratch your own itch' is given as advice because it leads to better solutions which lead to money. You are your own target market which makes building decisions and selling easier. It gives you drive & motivation because you know if it's something you'd use yourself or not & you have your first customer from day 1 (yourself). Trying to build something for a group of people you're not part of is tough and often results in a lot of guess-work.
One problem I'd like to see a solution for is for enquiry/quote based service businesses. Tracking which advertising method brings the most enquiries/bookings long term for small businesses. Also with reminders to follow up the following week after a quote is sent. This currently has to be done by combining several systems (analytics, gmail, calendar, spreadsheets, handwritten notes) this could easily be improved & simplified.