The weight carrying capacity of the springs is such that it recovers from bouncing quickly - but if you were to ride in your boat while it was being towed over rough terrain, you would find that it is an extremely rough ride - kind of like a corvette on the "performance" setting. They dont' put shocks on them because there is no need to - you don't ride in the boat on the way home, thus the ride doesn't have to be "plush". It's actually rather harsh - thus my reasoning for the transom saver that I recommended - the Lock N Stow. :lol:
I've only seen one boat trailer ever with some type of shock system, and it really wasn't a shock - it was a hybrid spring loaded type deal - on a Stratos trailer. Didn't work as well as the springs on a regular trailer though, and I think the newer trailers come with springs from Stratos.
All the best,
Glenn