It is a fact that a lot of people live a very long way away from an Apple Store, and so it's easier to have the device shipped to them rather than drive/fly themselves across the country to try it.
Most people might not buy things just to try, but there are countless examples of people that did just that in these forums alone, and I find it hard to believe that it will be limited to this readership.
Saying all that, the only people that will ever know the total number of sales/returns will be Apple, so there really isn't much point arguing about it, is there?!