Distinct sound design is useful for all players, but can also be an extremely helpful reinforcement when it is difficult to distinguish things by other means.
Some games can even be playable by gamers who have little or no vision at all, if key sounds are all distinct. A famous example is Brice Mellen, a blind from birth gamer who defeated Mortal Kombat creator Ed Boon at his own game.
More information: Interview with blind Mortal Kombat and Injustice player Carlos Vasquez
Best practice example: Injustice: Gods Among Us