Lore incoming boys
Masaaki Ishikawa: The most important thing for us is that it's more fun if the arms extend. So that's what we did. We are preparing a proper background story though. Don't worry.
Masaaki Ishikawa: It's a matter of priorities. Fun is more important than anything. The setting and the story has be fun too, but has to be subordinate. I'm thinking about backgrounds and stories, but if it gets in the way of the game – it has to take a back seat. We have a lot of fans that really get into the lore of the game. That's a powerful thing.
http://www.glixel.com/interviews/because-nintendo-arms-producer-explains-why-characters-have-stretchy-arms-w487949