Many, Many and the VAST MAJORITY of trailer manufacturers do not balance the tires on trailers since there is no real reason except to make one feel good to do so.
Larry
True this ...especially using the usual static tire balance machine that is used to balance our tow vehicle tires.
Which can actually make a tire/wheel and hub ass'y more out of balance depending on where those lead weights are placed on the trailers wheel.
Trailer leaf spring suspensions are very stiff and short 26" length leafs which act as a huge damper for any out of balance conditions on a new tire. Some folks point to a tire on a empty flatbed trailer jumping up and down at highways speeds. This is a faulty tire condition and no amount of lead weights will ever make it stop bouncing. BTDT when I was on the road. In my business we had no reloads back to the yard....so we pulled empty trailers back.
There are several reasons the industry over all doesn't balance a tire on trailer axles.