I'm pretty sure most obese children and adults were not carried in slings, I very rarely see anyone else using one.
I am also a little shocked that people can't carry some fairly light children for any distance. My one year old can't walk yet and he's 28ish lbs but I have no problem carrying him with a hip carry. As I'm pregnant he can't go on the front anymore but I'm getting a back carrier for him soon, plus planning on carrying him and the new baby at once.
Children get tired, I'm still going to need to carry him some distance when the baby is here and the only way I can see to do that is carry them both. He hates his pushchair and always has and I find it irritating to lug around, it gets stuck in shop aisles and doorways and would have to be left somewhere if I needed the loo.
The issue seems to be that people think it looks stupid rather than any actual concern about a strangers back or a child's independence. My dc is one of the most independent children at all the groups he goes to, other mothers who don't use slings often have their children clinging to them and refusing to go and play so I have no concerns that I'm forcing him to be dependent on me. I pop him on the floor and he's off, he might come back briefly to rest his head on my leg for a second and then he's off again.
I fully expect him to start walking once I'm very heavily pregnant, and then refuse to walk when we're out with the baby. What should I do then? Cart around an empty pushchair on the chance he might get into it? I'm carrying the baby as I believe it is best for them to help get used to the world and helps them feel secure, I can't carry toddler in my arms with them in a sling very easily.
It doesn't affect you personally if someone else carries their child, but it is upsetting to know people are so judgey of me! I don't go around thinking people using pushchairs are terrible parents, I don't judge them so why should they judge me?