In many jobs, if you finish your task quickly, you don't gain free time, but only more work. When I think back to my school days, it already started there. If you got a task in class and finished it quickly, you got another task as a “reward” instead of being allowed to go and play. But I don't want to have another task. What motivation is it supposed to be when working fast is rewarded with even more work instead of being able to take the rest of the day off. I have an office job where it has never happened that someone said I could get off work early because I was done with a task. Instead, they looked for a new task right away, even if the purpose of the new task wasn't always clear.
Therefore, I call for the Slow Work Movement. Do your work thoroughly, do it properly, do it on time but don't do it quickly! It is not worth to be ready days or hours before the deadline!