Part of the reason why is most motorcycles except the big classic touring bikes have large margin of Gross Vehicle Weight to haul a "modest" size trailer. Yeah, yeah...but before you yell at me, the aftermarket does gamble with this as they DO offer different rigs and hitch mount assemblies.
But in the final analysis...the onus is on you to determine if the selected combination will work...THEN the hard part begins, getting it registered,certified, insured and all that goes with that. Small wonder few under take this endeavor and honestly I applaud any effort to do so.