[quote=@Abillioncats]
Well sure but, Thor is literally his name. 
[/quote]

Yes but because he didn't pick something else when he joined the Avengers it is also now an official title, essentially the one who wields Mjolnir is The Mighty Thor within the Avengers. He'll always be Thor as that's his birth name but whoever holds his hammer gets more than just his powers, they get his name in the eyes of the public as well. Which sort of sucks for him.