I have noticed that the wind mills are generally planted in empty fields with no trees around, and I've been wondering why...

A wind mill is generally way taller than the trees and I can imagine that the trees don't actually affect the flow (see picture).

But is this is reason why there is nothing around or is there something else that makes them waste so much space around? And would this be a realistic velocity profile?

If I search for the theory of external convection, the velocity profile looks like this for flow over a plateau:

In the second case, wouldn't the velocity be higher if there is an obstactle? Or is it because the obstacle is a porous media that damps the flow? And lastly, is the velocity profile at earth level like that? Is there really an origin to it or it is fully turbulent and with different sources?