Nintendo explains the tradition of why their characters rarely speak.
Nintendo's heroes such as Mario, Link and Samus rarely ever speak, aside from the old 'Wahoo' and other grunts. It is rare to find a Nintendo game with recorded speech; however Punch-Out!! on the Wii had it. The game's producer, Nintendo's Kensuke Tanabe had this to say:
Nintendo's tradition is that the hero or central character never vocally speaks. The player's fighter, Little Mac, does keep quiet, as Link, Samus and Mario mostly have before him. We also followed this tradition for the title.
Nintendo's developers have said that they don't want to spoil the player’s imagination of how the heroes speak. In 1997, the old Star Fox crew spoke quite a bit in Star Fox 64 with some of our favourite one liners "Do a Barrel roll!" still memorable to this very day. Metroid Prime 3 also had recorded speech.
The voice work in Punch-Out was used to give its NPC's more flair. "We recorded speech to express each character's origins and characteristics, and to make Doc Louis have a larger personality and greater impact on gameplay," Tanabe said. "I believe having fighters' voices during matches is very effective in making the experience more immersive."
The Canadian development studio backed up Tanabe's comments. Next Level producer Bryce Holliday said:
There's a nice dynamic to the quiet hero in combat against massive, talkative foes. Since we used the original camera view from over the shoulder and kept the feeling that the game is about overcoming your fears and knocking out your bullies, it makes sense for Little Mac to talk very little. He is more avatar than character, giving fans an opportunity to put a little of themselves into his character.
So do we want to see Link in his next game chatting away?