Space, not weight, is the main concern. The RV is heavier and is capable of being overloaded. Also the storage capacity in most RVs offers any number of possibilities for improper weight distribution. Loading your supplies can have a major impact on how the vehicle handles, as well as on the durability of your tires. The results of overloading can be serious.
Passenger safety is at stake.
The entire vehicle with all wheels on the scale. Front axle with only the front wheels parked on the scale. Rear axle with only the rear wheels parked on the scale. Left side with only the left front and back wheels on the scale. Right side with only the right front and back wheels on the scale.