What is interesting is that scotchloks made for the telephony industry actually work very well with a pretty low failure rate. However, they are used with 22 thru 26 gauge SOLID wire with insulation designed for this purpose, AND they are used with the tiny communication currents in stationary service not a moving trailer and are not subject to the elements usually. They are in a pedestal or if underground are encapsulated in a large cocoon of a rubber like substance poured in as a liquid. Plus those scotchlocks have a jelly like waterproofing compound in them that flow out around the wires.
I don't know who thought they or similar products would be a good idea in the trailer wiring industry. But someone did. If they had to account for all of the lost man hours of people laying in the mud under a trailer trying to repair the dang things in the middle of the night, they might think differently. Twisting the wires together, soldering and the heat shrink tubing with the goo inside, sounds like a good solution to me.