Different players and different reasons. Think of it this way, any shop has a quiver of ways to make money. Question is, is it enough money to bother with, are there better places, who is doing it, the veterans or the interns, how ripe are the opportunities now versus later.
So in the details you will find the specifics. And in those specifics you will find which are action-able and which are not.
Penny stocks take small amount of funds to move the price. But also don't have much "meat on the bone" either. It is a matter of $/effort/results.
So again, generalization, rarely help you trading and are rarely actionable.