That's true, but humans are generally creatures of convenience and follow the path of least resistance. Today people are forced to walk in many situations where

That's true, but humans are generally creatures of convenience and follow the path of least resistance. Today people are forced to walk in many situations where they have no feasible alternative (can't afford it, transit doesn't go there, etc). It seems pretty evident that, on the whole, the proliferation of these devices will contribute to less exercise and more obesity.