It's a game, it's supposed to be fun. I'm glad there are difficulty settings on some games, I always try to make sure the game is challenging, but enjoyable. In order to make a chance with Mario Kart, I have to ask my friends to drive on 50cc, when we're playing Mario Party, we'll put the computer on hard, else there'd be no challenge.
Saying things like "real players play more challenging modes" is just a load of crap to me. If I think easy mode is more fun than hard, who are you to judge that.
I think that adding difficulty also adds to the replay value of games. You can play a game on easy if it's your first time, and when you feel like replaying it, increase the difficulty to keep things interesting.
One thing I don't like is something I've seen with games like Golden Sun2, and Pokemon bw2, in which you have to finish the game first, before you can unlock easy/hard mode. -.-"