Why is it that some players are missing from nhl 17 but have been in other nhls

Why is it that player like daniel alfredsson and wayne grezky are not in nhl 17 but have been in some of the other game? I know there is probably more players that are not in the game anymore but i would love to see at least daniel alfredsson as ottawa senators hut hero cause i grew up watching him play and i believe he was one of the best players we had on our team