Because it was made by company who made Elder Scrolls? Of course they make Fallout the way they do it best.
Both are their franchises now, and given how popular some elements from Fallout are, particularly the perks, I don't see why they shouldn't copy them over. For most players, Bethesda made Fallout too, and they know Fallout only from Fallout 3 and New Vegas anyway.
Wait...If we disagree with you, we're automatically as bad as NMA?
You disagree not because of any objective arguments but because "it's from Fallout" or "it shouldn't be in Elder Scrolls", just like people who hate Fallout 3 because it's "Oblivion with guns".
There's a difference between 'change' and ripping off a piece of a game and pasting it on another.
It wouldn't be a rip-off because they own both franchises. And they pasted a lot of stuff from Oblivion to Fallout 3.