They would be better off and the roads a lot safer to drive on if they gave NO information if the customer's tow vehicle was capable of towing a proposed purchase. Customers need to do their own homework just like purchasing any other item you are not familiar with. Just saying.
Interestingly if you go to buy a horse trailer which go from a 2 place up to giant 6 place LQ fifth wheels, where you know that each and every item you are going to put in it will weigh 1,200 lbs each added weight to the trailer........salesman rarely say and/or ask squat about the tow vehicle.
Maybe because horse people know what they can or can not tow and always err on the side that a bigger over the top truck is 'always' better! :W