I never really thought about high traffic areas needing something like grassy pavers. Now that I consider it, regular grass on the ground would wear down with the weight of automobiles and foot traffic, and the soil beneath could wash away in a rainstorm.
This makes me think of the trails that cows make in the pasture beside my house. Cows are quite heavy, and the paths they travel often are flat, though the grass and weeds grow tall along beside them.
If they had grass planted straight into the ground, I suppose parking lot grass and soil would give way to the pressure of tons of steel before very long. Grassy pavers sound like a good alternative.