This is the way I see it...
I figure if the boat is resting on the bunks(properly) and the boat is attached to the trailer so it doesn't move off the bunks,the springs/tires will absorb the bumps in the road.
Theres no more weight on the stern weather it's on the trailer or in the water(cracking on etc.)
I tow with my outboard locked down,bungeed to one side so it doesn't move much.
That's why it's important to have your bunks strong enough,plus long enough to carry the transom.
Had a 40hp on this boat,now a 30hp...no transom saver.
If I had to tilt my motor to tow,then I'd get one,more to save the outboard not the transom.
Just an opinion.