By that logic glass armour should be better than Dragonscale, which I'm sure isn't the case.
Who knows, it may well be.
The only reason people seem to think dragon bone should be better is because it requires 100 smithing, when daedric requires 90. At this point, you must note that dragon smithing is both light and heavy armor, and it available no matter which direction you choose in the smithing perks. Daedric can only be obtained by going the heavy-material path. Sure, daedric smithing could require 100 smithing and dragon smithing could require 100 as well, no problem, but bethesda apparently wanted there to be a very specific progress in perks and that you can't go from a 100 perk to a 100 perk, much in the same way as you won't go from a 20 requirement perk to a 20 requirement perk; the progress needs to be there. Simple design choice, nothing to rage over.