I believe Achievements have a major role in social gaming. so to me any gaming platform that allows you to have friends, look at what they are playing, game library, etc, needs something like this to show the accolades of that particular gamer.
At the same time this is Nintendo we are talking about. they will not just simply do something like trophies/achievements, they will make whatever you achieve usable in some sort of way. like the stamp concept from Mario wii u games, where you can leave messages for others and design things with these achievements you collect.
and as turf mentioned it is a no lose situation putting them in.