Lack of time. Assuming you work a day job to pay the bills, there's a fixed amount of time left over to work on the side project. And that limits how much "stuf

Lack of time. Assuming you work a day job to pay the bills, there's a fixed amount of time left over to work on the side project. And that limits how much "stuff" you can get done in a given calendar period. And that can be very frustrating mentally, when you see other people working on the same (or similar) ideas, and they can move faster because they're funded and have full-time people working on it. OTOH, there's another sense in which you can move faster than competitors, in that you have less inertia involved. If it's just you (or you and maybe one or two other people) you can potentially switch gears and change directions much more quickly than larger companies with more people involved.