Did Johnny Depp dress like this because of the grunge era, or did people involved in grunge dress like this because of Johnny Depp? We may never know for sure, but we do know that Depp looked especially iconic back in 1990.
You may think you've seen Depp with long hair plenty of times in the 'Pirates of the Caribbean' movies, but you haven't. He was wearing a wig in those films, whereas back then, his hair was very real.