Completing a thing your start is important. It gives you fulfilment in itself. Also, A complete thing can be presented, sold, or used. So when it gets used you get the benefits as well.
In contrast, if you leave a thing incomplete, move from one shiny object to another, it only gives you dopamine for the instant, but do not help you go through form point A to point B.
Not completing a thing also has its importance. It is important when you are just checking out something or when you are doing it as a hobby.
So here comes the next point. the difference between the Hobby and the thing you do for living.
More:
https://fazalurrehman.com/overstimulation/