Why do the characters look like their voice-over actors?

Rating: Null/10 (7 October 1998)

I read in Entertainment Weekly a while back that when the animators first started this film, the character of Z looked "too much" like Woody Allen, and the animators had to change Z's look several times. They succeeded in their attempt--in the movie, Z doesn't look much like Allen. My question, however, is why do some of the other characters look like the actors that provide their voices? The ones that stand out the most are Weaver (Sylvester Stallone), Barbatus (Danny Glover) and Azteca (Jennifer Lopez). Of course Barbatus "looks" like a black man--how stereotypical. I'm not a big Jennifer Lopez follower, but I swear I'd recognize those lips anywhere... What happened to the creativity of animation? Isn't it more fun to "figure out" whose voice is bringing life to that animated character rather than having it "shown" to the audience? I know Sly's voice is pretty easy to identify, but so is Allen's--the creators obviously put some work into designing a unique ant look for his character, a look that made the movie more interesting to watch. Come on, guys--this is what you're paid for! Give us a creative look of an animated character, not just an "cartoon" Stallone!