It has to do with the laws that govern trailering in different counties. I'm not sure on the restrictions in place in AU but in the UK one can not tow more then 2000lbs without trailer brakes, they can not go over 60mph and the tongue needs to be weighted a bit differently. There is also much stricter licenses needed to tow. Conversely, here in the states there are very little restrictions on towing until you get up to around 10-12K lbs and require a CDL license. There is no additional speed limit when towing either. 8000lbs at 75mph is a lot of weight at a high speed with out any special training or experience. Its all the lawyers say for what can be towed. Example in the US the CX-5 is rated to tow 2000lbs but in the UK it's rated to tow 1800kg = 3968lbs. Same vehicle, same engine, same transmission, different laws regarding towing and safety.