Why do people care to make comments on a pregnant ladies weight?!!

From friends, to family—like what do you expect?? Everyone/every pregnancy is different...it’s so inconsiderate to make jokes of how “big” a pregnant lady has gotten. Yes Susan, while I am gonna use the pregnancy card for my weight gain, what’s yours?! Even my MIL has commented on how she thinks I am gonna have a big baby because of my huge belly size ...like I wish I could slap her and all people who make jokes or inconsiderate comments towards pregnant ladies (especially women whom already have children, shame on them!)