Lots of TTs have torsion axle suspension instead of leaf springs. My cargo trailer has Dexter TorFlex axles and therefore doesn't need shocks.
But my TT came with leaf springs and no shocks. I added shocks shortly after my first long trip with the TT. And towing differences are very subtle, but stuff in the trailer tends to stay put with the shocks, instead of being scattered all over the trailer after a rough ride.
Installing shocks on my trailer was no picnic. The welder/fabricator had to fabricate new plates for the bottom of the springs and include a bolt sticking out for the shock to fasten to. He then welded a gusseted bolt to the frame for the upper connection of the shock. Here are the shocks I installed:
Amazon.com: Monroe 557003 Gas-Magnum RV Shock Absorber: Automotive
Works great now. We made a 4,500 mile trip in November without any problems with the TT.