Motivating people is hard damn work.
Motivation wears off after an hour or a day or so, so if you're the motivator, you're always working. You can't use the same motivation too much since its effect wears off, so you're always finding new things to get people going. People who need to be motivated usually have good reasons to not believe the usual motivations, so you have to fight against that current.
All of this takes place before the now-motivated people get anything done. It's time and energy consuming, like pushing a boulder up a hill.
What if you had some people who were already motivated?
All the time and energy could be preserved and used for actually getting stuff done (since motivating people doesn't produce an actual result). You would have to manage and direct less, since motivated people usually take more initiative. Even clueless motivated people will be eager to learn, and useful for their energy in the worst case. Working with the motivated is like pushing a boulder downhill.
None of this can happen with unmotivated people.
So what if you dumped every need-to-be-motivated person around you and only sought and dealt with motivated people? Regardless of skill or experience level. You would save time and energy and get more done by default. Add in some skill and you'd be unstoppable.