ST or Special Trailer tires cannot be used on a driving or a steering wheel. This means they can't be used on 2 or 4 wd vehicles. Technically they could be used on the back of a front wheel drive vehicle, but not on the front.
Over the road trucks use tires designed for the specific mount, be it driving, steering or trailer. I believe they can be cited and ordered off the road if the wrong tires are caught at an inspection station.
And yes, we did some pretty silly things back in the day, it's a wonder that this many of us survived those vehicles and our ignorance.
I.E. I pulled a 25' Airstream over 25,000 miles with a 1972 Blazer in 1977 without a thought to tongue weight, towing limits, etc. Although my new bride did learn, that if the trailer brakes
aren't set correctly, that it is possible to swap ends at 55 MPH.