You can't use heavy machinery under the solar panels, so the crops mainly need to be tended to, and picked, by hand. So farmers are limited in choice of crops. All corn, canola and cereals are off the table, once these panels are in place.
I've seen some fields with solar panels used to raise sheep.
The better question is, why isn't every car park covered in solar panels?
På Statens Museum for Kunst, var der engang en cafe, hvor der var sat frem til at man kunne lave bloody Mary ved deres brunch buffet