The idea was that they living banal lives similar to that of farmyard animals, though, yes, we do seem to have been beaten over the head with the concept. I actually prefer their realisation in the concept designs prior to modelling. They still looked like chickens, but decidedly weird chickens.
What gets me most is their wings. The other species on Oddworld have a skeletal structure that makes sense, but clakkers use their primaries as fingers! I'd prefer it if they had given them birdlike claws for hands, much like Chris Riddle and Paul Stewart. did with the avian
Shrykes in the Edge Chronicles.