They do have to but not in anywhere near the same way.
For starters you won't find a ford dealership selling second hand fords right next to the new ones.
Next you've got the fact a second hand game is functionally identical to a new game, unlike a car a game does not degrade with age beyond being damaged by the owners in which case they won't be sold anyway.
Also when was the last time you bought a second hand DVD or CD from one of the major retailers or supermarkets or even saw them for sale?
Did I not just say I was fine with physical copies?
Just for reference I am generally against the current state of second hand game sales, however I consider it a problem as a result of the high prices of games. Unfortunately the reason for the high price is actually justified due to the much smaller demographic of games compared to the only realistic comparison to the games industry which is film, film has multiple avenues for profit such as cinema, rentals, tv all on top of DVD/BR sales.