This is true in every sector of work. People are motivated by success. As a marketer who manages a team of 8 (including myself), I've been trying to learn to a) give context into why I might be poo-pooing something and b) a few ideas for other directions we could go.

Part of the job of being a mentor and manager is to guide them in a helpful way to greatness. Allowing them to work on whatever they want to work on is no way to build someone's confidence and skills, let alone a business.