When is weight distribution needed?

Forty years? I started out on the farm over fifty years ago and progressed through forty years in the construction business towing with everything from a tandem dump with a pintle hook to Ranger pickups hauling backhoe buckets on small trailers. Believe me, you know what sway is with a thousand pound backhoe bucket behind a Ranger. By the way, sway is not front end lightness but overloaded rear suspension. WD hitches are the first thing people go for when they have an overloaded tow vehicle, and they can help. Helps even more to get a tow vehicle rated to tow the load without any need for a band aid.

Having said that, if you "Think" you need a WD hitch, get one. Salesmen love them.