I was around when all this happened. The first builds of the game when it hit closed beta (Feb / March 2013) had all the UI elements in them and they worked flawlessly. Name plates, combat logs, SCT etc etc..What dumb fucks. Then add the basic shit to the default UI and put everyone on the same page. This is why listening to player-base is so retarded. From what I heard the original UI in game had all the basic information, but players whined it wasnt ES enough so they removed it and addons had to take their place. So why the fuck would they make changes to appease a audience that doesn't want that information at all, even when its given to them in the default UI. How the hell does making it a addon, suddenly compel them to want it again. Just another case of certain players not happy enough to play their way, they want everyone else to play their way also.
What happened was many people were not happy with the game and said "this isn't an elder scrolls game" with a list of complaints:
World is static
Questing linear
Not much stuff to grab
Combat was terrible
etc..
The developers essentially started stripping UI elements out of the game (slowly over the course of 2 or 3 months) and said "See we made it more Elder Scrolls like" despite people pretty much hating it. I remember early polls on the CB forums showing 90%+ of the players not liking the changes and they didn't give a shit. I don't remember ever being in a closed beta with that many players agreeing on anything.
Right around then (End of May / June) was when people starting bitching about the developers not listening to the players and we got the "we have a vision and have internal metrics thank you but no thank you for your feed back".
They were unable to change the game to make it anything close to ES so they did the next best thing and changed the most visible part (UI) which also happens to be one of the worse things about the series. They doubled down on stupid and are continuing the trend.