Govt has been mandating tire pressure systems on cars/trucks for around 15yrs and aftermarket systems for trailers are also very popular, so apparently, someone feels underinflation is an issue and constant monitoring is important.
Most people who switch have no baseline to compare to. It's only after the blowouts that they start randomly trying things to improve the situation...like checking the pressure regularly (or adding a TPMS) or actually getting the RV weighed to make sure they aren't overloaded. Then they switch to LTs at the same time...low and behold, they are less likely to experience a blowout but never systematically tested to see what fixed the problem...then again blowouts are pretty rare to begin with so their changes may have zero impact.
Once you switch to LTs there is a bigger selection but that is mostly about tread patterns (and profitering). For a trailer, there isn't a lot of benefit to off road tires, so little reason to provide a wide variety of tread patterns in ST tires.