That is true, until you have your legendary power in two slots without dom sockets. You craft it and next week you get an item from the vault in that slot with BiS items. Now you can choose to either spend weeks recrafting the same power in a different slot, or go for different legendaries.
All people want, is to be able to swap their legendary to a different slot for a small Soul Ash fee (let's say 1k or something).