Because comparative advantage. Do what you are good at, and pay for what you are not good at. Spending time on learning has an opportunity cost. If your opportunity cost is low i.e.: your current income is low, then maybe learning to program is a good idea. But if you make 200$/hour, you are better off finding a technical cofounder or outsourcing it. besides, having a technical cofounder lets you focus on other areas of the business. At least this is how I see it. The Woz/Jobs tandem would be a paradigmatic example of this.