Locking (wheel) hubs could certainly be used to disconnect the wheels from whatever drivetrain trouble lurks within, but they come with a whole lot of compromises: cost, weight, complexity, space, etc. Standard industry practice for vehicles that can't be towed with only two wheels immobilized is (and has been for decades iiuc) to flatbed tow them, so Tesla isn't really going against the grain here. I think it's a fine choice.