I don't think the devs will implement this since it will become a heavy abuse once its implemented. the answer is pretty obvious
Think of it like this, as a cav player you can ride horses around, sure but the AIs are dumb, if one cavman ride around the AI in circle the AI will endlessly follow him around unless the horseman go to other directions or he dismount. while he is doing this some players especially ranged can pick off some lone AI/ AI that are stuck to to wall / shoot them from a safe distance therefore making it incredibly easy to play DTV.
since you are not allowed to have horses on DTV the devs should change riding into ath. so players who have ridings without ath will have some ath since horses are not allowed on DTV. its only fair right?