The I don't use them argument is really from another planet.......

Once upon a time you actually got a dollar or 2 back when you returned a Smarte CArt, the problem was that this attracted masses of homelss who often physically fought over the used carts, so was discontinued, but the prices not dropped.

The "deposit" system is quite effective, but only if the airport maintains a decent amount of personnel, the problem being that if they do not, all the carts accumulate in one place eventually as there is not enough staff to adequately redistribute them.