Why do motivation and purpose related so much? In my opinion our brain has a way of rewarding itself after doing certain work. If you don't have purpose, your brain will reward you even after you perform a small task.
After the rewarding, we would want to step back and relax to get ready for another job. Its not a bad thing, but if it occured after very small things, what a long way to go to accomplish big things.
Motivation is very important in the workplace, because it sets you purposes. It shaped the culture of postponed rewards. So it doesn't take you away from your rewards, but it postponed them until you get to the purpose.
The problem with motivation is, the risk of not being properly rewarded after you accomplish your goal. So it took professionals to give the format so that the storage of rewards wouldn't leaked out and caused insatisfaction after achieving.