I'm guessing it's nostalgia. The bananas in the original game had stickers on them, but the newer games didn't. There are a lot of people who love the old SMB games and are happy when anything is done to make the new ones like the old ones.
I don't get being so excited about it, but these games weren't a core part of my childhood. I played the party games in SMB 1 once and those were fun, but I don't think I ever actually played the main game.
The same reason I hope CalorieMate stays in MGS 3 Delta, it was in the original and became a part of the identity of the game. Not having it would feel weird.
Kinda like when something gets remade and is nearly completely different from the original. All the right names and pieces are there, but its off and doesn't feel right. 2010 Nightmare on Elm Street stuff.