Because Dark Pit is a great, sympathetic character and I suspect most (not all) of the people who are so salty about him have not played Kid Icarus: Uprising or didn't like it. He's really cool in Uprising and it's made very clear that he's much more than just a mirror image of Pit.
I can't help but laugh at all these people being so salty about Dark Pit while they hype up Dr. Mario and lament Wolf's being cut in the same breath. Dr. Mario is literally Mario wearing a doctor's coat and is an actual, literal clone in every sense of the word. Dr. Mario is just getting a dumb pass because of his Melee alumni status and people are simply salty about Dark Pit in the exact same way they were salty about Wolf in Brawl. The more things change, the more they stay the same.
I don't know exactly what Dark Pit's FS is, but I read that it utilizes his staff.
I've beat the game, several times and did the square challenges. I love it to pieces and it's one of my favourite 3DS games. I love the storytelling in it, I love the characters in it.
But Dark Pit is the worst character of the whole game, by a long mile. He is derivative, his atrocious, has the charisma of a wooden plank (that stands out even more because ALL the rest of the characters are much better than him), and only worked as a joke of the typical dark version of characters in games and cartoons, that try to be edgy to 12-15 year olds.
So I dont know why are you "laughing" so much to a lie you have just invented.
Do you want me and other people that criticise him to take a photo of the game to show you more prove?
Most people don't see him cool or anything like that, we know what up with those type of characters. If you think he is cool, good for you, but let the rest us complain what a shitty addition he is to the roster.
His addition married with the absence of less "clony" characters and more important than him, seriously bring the good roster that we got down.