http://www.polygon.com/2014/5/27/5754590/mario-kart-future-rosters-super-smash-bros
Yabuki added that he had to have series newcomers the Koopalings Bowser's seven rambunctious minions all appear together in Mario Kart 8; splitting them all up and only including a few was not an option. The director noted their inclusion was because of their "superb individuality" and unique expressions. These seven have replaced a handful of previously-included characters Bowser Jr., Dry Bones, King Boo and Diddy Kong for which Yabuki apologized to their fans.
"Were always considering ways to make the Mario Kart games more appealing, but I dont think that just increasing the number of characters would make the game better," he said.