cause getting dragon stuff is much easier then finding daedric hearts and ebony ingots...
I hope this is sarcasm. You will usually have enough dragon materials already to make what you need by the time you reach the skill, but it's extremely easy to get enough Ebony for an entire set of gear, including two swords from a single mine. The hearts are also extremely easy to get, and are sold for ~900g at the Mage's College.
The reason to even hit 100 in Smithing is because your smithing level does affect how much of an upgrade you get when you upgrade a piece of gear.
Another thing, is, it doesn't matter what armor you are wearing. Even scale armor will cap you out once you have 100 in the appropriate armor proficiency. Nothing beyond 580 AR does anything at all, because it's the cap. So wear whatever armor you think looks the coolest.