Each of those cars is being resold for the first time, most likely. How many times is a car sold in its lifetime? Eventually it's sold to a scrap dealer for $500, and I'd bet that transaction is not included in the 15k average.
In any case, anyone considering a new car and concerned about depreciation should consider leasing instead. That way you only pay the depreciation (which you'd pay anyway) and after 3 years you have the option of buying it as a used car for the remaining cost or moving on to a new car with no hassle trying to sell it.
In any case, anyone considering a new car and concerned about depreciation should consider leasing instead. That way you only pay the depreciation (which you'd pay anyway) and after 3 years you have the option of buying it as a used car for the remaining cost or moving on to a new car with no hassle trying to sell it.