What really pissed me off recently, is that after deleting my FB account, whenever I login with email/password to a web site where I previously connected my FB

What really pissed me off recently, is that after deleting my FB account, whenever I login with email/password to a web site where I previously connected my FB (Spotify, for example), it restores my FB account without asking me and tells about it to my FB friends. Why the hell does it even keep a list of friends if I deleted the whole thing?.