Wood or rubber can work to add grip to the transom for clamp-on type motors, and to dampen vibration for bolt on motors.
As one who has had more than one motor work it's way off a slick aluminum transom when making a hard turn, I'm all for making sure the motor is secure!
Some boats have a wood pad, some have a rubber one, and some have a piece of flat metal with the top edge bent out about 1/8" to catch the feet of the motor clamp . All of them work. Just make sure the pad is secured well to the transom.
I ALWAYS have something on my transoms to secure the motor! It's a bad feeling when suddenly the motor pops off and you are holding a running motor in your hand!