how else would you describe him? "Rock star Paul McCartney" is hardly enough; it'd put him on a par with "rock star Jon Bon Jovi", which he certainly isn't. You describe people by their most significant characteristic, and that's Beatle membership. (Same for Ringo.)
Alternatively, you could not describe him at all; but that's a bit of a non-starter for the media, who need to explain exactly why the story they're telling you is important, This means identifying the people in it.