Fame
You know Edison, and Tesla, and Einstein from school, right? How about Charles F. Brush? James Blyth?
Windmill inventors seem not to have fared so well as the big-name innovators. The last time anyone gained notoriety from a windmill, it was the early 1800s, they were wearing Dutch clogs, and they designed the windmill while walking through a field of tulips (source). There's also the three millionth most popular tourist destination (an approximate ranking) in Spain: the "legendary" Windmills of Castilla-La Mancha, depicted in Cervantes' Don Quixote.
Even as the world turns to wind energy, it doesn't give one collective hoot about who actually made the windmill. You might get a small profile tucked away in a corner of The Sail Away Journal for Kids, but don't expect to be on the front cover of TIME magazine anytime soon.