Most of the rigs are fifth wheels because it’s legal to tow a boat behind your fifth wheel. You can tow a boat behind your motor home but not both a car and a boat. There are some travel trailers also followed by boats.
Notice how "boat" seems to be the major connection here. We aren’t talking sail boats or kayaks. We’re talking fishing boats. Some more powerful than others so they can beat you to their favorite fishing spot. But all are fishing boats. The men also outnumber the women but there are definitely some fisherwomen. However, that would not be me.