Well the feather weight limit change was to match the states. 12kg to 13.6kg (30 pounds)
Seemed logical and was quiet an easy transition.
Beetle weights are really more popular in the US and not matching their weight would cause some issues in traveling over. Though thats not very common.
Also numbers are quiet easy to remember if you work the other way. Feathers 13.6kg, beeltles 1.36kg