Remember how Don Quixote was fighting windmills because they were "giants oppressing the people"? He was right! And everyone in Cervantes' day knew it.
Windmills did not, contrary to popular belief, mostly spread as convenient labour-saving devices. Instead they spread as a way for the local lord to enforce taxes. When peasants had hand mills, there was no easy way to see how much food they really had grown, so it was hard to collect taxes. But if they go to the local miller, the miller takes your grain, grinds it, and then takes the lord's cut right there. There is no possible hiding of the food you've grown.
In countries with a strong peasant class, like Sweden, the lords were unable to introduce this form of central taxation. And I've read reports that hand mills were still in use there as late as WW II.