You also have to account for the fact that it was only "recently" (comparatively speaking) released on Steam compared to how long the game was released previously. The fact that they don't allow you to register the game on Steam if you already acquired it directly from ZOS has to be taken into consideration here, IMO.
TL;DR - If you got this far without reading the entire post you're either too lazy or suck at reading comprehension and probably don't belong in a public forum anyway. Just move along, you wouldn't understand.
Is there really any benefit to playing through Steam?
Steam achievements, trading cards, overlay, and of course show all your friends how much time you have wasted into a game.
AKA "I have no life." metrics?
TL;DR - If you got this far without reading the entire post you're either too lazy or suck at reading comprehension and probably don't belong in a public forum anyway. Just move along, you wouldn't understand.
The big advantage of Steam is that your software is stored in the cloud and not on your computer so if your computer crashes you don't lost any software bought on Steam; by comparison, if you bought a game DVD and lost the DVD, your out of luck!
The other advantage of Steam is that the software auto-updates so you don't have to worry about patching it.
I would like Steam to support addons in ESO using the same system it uses for Skyrim Mods where the addons could be selected from a workshop and then auto update.
The disadvantage with Steam is that steam software is not transferable, or can not be resold, and Steam software cannot be returned PERIOD! Some major software titles do not integrate well with Steam; for example, the Rocket Star Social Club games cannot be easily unlinked from a Steam account without putting in a support request which will months the resolve.