I already answered that: I've had to take care children before and logical arguments like "the sooner you get your chores done, the sooner you can play" doesn't work. If they don't want to do their chores, they'll complain, drag their feet, procrastinate, do the work as lazily as possible dragging a task that could have been done in minutes into hours, and the instant they think they can get away with it, they'll try to ditch the work. Goku is pretty much a big kid. It seems in-character to me for him to act like a child to get out of work. Goku did do farm work using bare hands under Roshi, but that was part of his training to strength his body. Goku has long since past the point where he could get any benefit in his training for that. Goku isn't interested in money or in farm work; he just wants to train. Since it is no longer effective training for him, Goku wouldn't be interested in doing that. It makes sense that he'd do it lazily out of boredom and then try to ditch it to train by having Goten do it instead. Goku is only doing this because Chichi is making him.