Since its introduction in Mario Kart 64, the blue shell has become a universal shorthand for the perils of video game rubber-banding; an item I called "scourge of the skillful and the great white hope of the novice" in my own Mario Kart 8 review. Targeting the first-place player with a nigh-unstoppable projectile from anywhere on the course is a perfect encapsulation of the series' focus on giving everyone playing a chance rather than letting pure racing skill win the day by default.
Love it or hate it, the blue shell is a necessary part of the game, according to Mario Kart 7 and 8 director Kosuke Yabuki. In a recent interview with Eurogamer, Yabuki said Mario Kart just doesn't feel like Mario Kart without the item.
"We're always experimenting with what new elements to introduce or what elements can be removed," Yabuki told the site. "We have tried—or we are trying—to see what the game's like without the blue shell. When we've experimented without the blue shell, actually it feels like something's missing. Like there's something not quite enough in the game. So for now we've kept it in."