Vendor weapons confusion

[SenKanashimi]

I understand that vendor weapons cannot be used as weapon skins, but what I don't understand is WHY? What possible reason is there for this? I wanted to skin my razor to the Raptor Iron dagger, but nope!

 

Why? They do less damage than the hongmoon weapon of a lower level and have no worth for infusion, so they are virtually worthless.

 

Please let them be used as skins ;-;