Their higher kick is part of their action. They don't get a higher kick, it is something they have.

Showing Up is a great example and I think even Barbaro is a good example. They didn't develop muscles to run on the turf, they just have an action that is better suited to turf racing.

Watch how many races are won on the dirt from the front and then watch how many races are won on the dirt from coming behind.

Horses develop muscles for running certain distances, not really for running on dirt or turf.