I would have answered to the poll if it didn't contain specific accusations based on an agenda the OP is trying to drive.
I will however answer more directly that i use MCCC to maintain body shape, so i can work out sims as i like or the game can spawn my played sims into the world to exercise.
TS4's weight gain and loss is hyper-unrealistic and what's worse, it's like these sims don't have bones and sims often work out until they have no pelvis at all (and it's most notable on male sims than female sims) as well as massive muscles, it looks absurdly ridiculous. It's like the developers never bothered to look up what exercise and overeating on junk food does to a body.
Using MCCC to maintain the shape of sims is the best thing going for it, at least they continue to look as they do and if i want sims to gain weight or lose it, i can do it in a realistic manner.