I have a rear luggage rack on the back of my 95 HD Heritage Softail and as I recall it had a sticker on it indicating max load limit of 10 pounds. Needless to say I've had 30 or more pounds on it for thousands of miles and no issues. Also if you look at the published load limits on the saddlebags of Harley Baggers they tend to be very low. My guess is it's the lawyers, the manufacturers know they will handle more but just don't want to have to defend that in court.