First off very few trailer arrive at the dealer at the brochure dry weight value.
THe brochure weights are notoriously incorrect because they are base on a stripped no options model that really does not exist.
If you want to get a better idea start with the ratings sticker that is on every RV. This is your real starting point. Keep in mind it is specific to the trailer it is on and that the sticker dry weight is generally not readily available on line. Your 10K brochure weight will more realistically be a 10,300-10,500 sticker weight depending on options.
My rig came from factory with 2 A/C's and a genset. My brochure weight was off by quite a bit.
You are correct that you may never fill trailer to max GVW.
But the cargo weight for everyone is different.
Some bring everything including pink flamingos while others are reluctant to carry an extra drop of water.
GVW is used because it is the worst case scenario and allows some margin for error.
If you know yourself and are willing to use scale vs. guessing using yoiur exact weight is doable