It is the same mindset of the founder "just looking for someone to build it". The though of learning it themselves, literally never crosses their mind because, they are not of that personality type.
It's akin to saying people that go into finance where worth their weight in gold in the 90's, why didn't you go into finance, may of us did in a way, but most of us used a wealth manager, broker, mutual fund to do so. Developers are like that wealth manager, they do all the technical work that investors do not want to do. Some people take the time to learn the models and self direct their investments, but they are the minority.
Most use a professional, though I doubt many investment professionals had to deal with the: "hey I have an idea I want you to build, I have no money, but I will cut you in for 10% propositions".