The trailer manufacturers provide over a million tires a year. If they used junk tires, you would see hundreds of TTs on the side of the road with shredded tires. How many have you seen?
Like the auto manufacturers they contract for the least expensive tire that will do the job. And, like the automobile dealers, if having a set of high speed Michelin’s mounted on your pick-up makes you happy; they will be more than willing to sell you a pair.
Likewise if you know better than the TT and Tire industry and think that ST tires are not as good for trailer use as LT tires, you will not be alone; and again the dealer will be pleased to upgrade you to about any tire you wish to pay for. After all what do those industries know, they just do these things for a living.
One thing is for sure, if you do not inspect and properly maintain your tires or to run over a road hazard; you will be just a flat as the next guy. Upgraded tires or not.
The best reasons that I have heard for changing either the TV or TT tires, is because the original towing combination did not perform well and a tire change improved the towing stability of the TT and TV combination.
You certainly will hear stories both ways but in the end the choice is yours.