There's nothing stopping you, true. But I think you will find that nobody is going to buy software for whatever thousands of dollars it took you to make it. So the limitation in this case is a practical one, not a legal or moral one.
Developer presents the idea and how much it costs. If enough people pitch in, then the idea is funded, the developer gets the money as a lump sum and can turn the idea into reality.
Why did this model fail?