I've heard a lot of rumors and theories as to why this is, from claims the voice actor quit last minute, and so on. But I read on a local media website an interesting article today.
http://www.stuff.co.nz/technology/games/6170408/Why-GTAs-Claude-was-silentOver 10 years since Grand Theft Auto III was first released, pioneering developer Rockstar has finally revealed why the game's hero Claude is mute.
The studio says it was only partly to "aid people identifying with him".
"It may now seem obvious that people should all talk in games, but this was not necessarily the case in 2001, certainly not in an open-world game," a Rockstar representative explains on the company's Newswire site.
"We were making up a lot of procedures as we went along, and we decided that the NPCs (Non Playable Characters) should talk and we would have to figure out how to make them talk (using motion captured cut-scenes, something that had never really been done before, at least not on the scale we were doing it).
"So we decided that the game's protagonist would not talk, partly to aid people identifying with him, but mostly because we had so many other problems to solve and this did not seem like a major issue."
Rockstar would later introduce a talking protagonist in sequel Grand Theft Auto Vice City, with players controlling Tommy Vercetti, who was voiced by Ray Liotta.
Just found that interesting.