I have wondered if children's diets precipipate this problem. Because so many kids grow up with varying levels of processsed or pre-digested foods (pulverized fruit pouches, not enough crunchy whole foods that require chewing etc) the jaw does not develop fully - so wisdom teeth removals and orthodontics for expansion seems like standard of care nowadays - but really it should not be that way. These cases should be rare but instead they are assumed common and normal. I quick search about this shows there is a relationship but I havent looked much into the details.
Look at the book 'Nutrition and Physical Degeneration' [1] by Weston Price [2], a dentist who travelled around the world in the 1930's comparing facial development and health of traditional cultures eating unprocessed diets to those who switched to a western diet.
There's also the more recent book 'Jaws' [3] looking at the orthodontic industry and ideas John Mew.
Genetics, lack of breast feeding, soft foods, etc probably influence poor jaw development. Also mouth breathing due to allergies and nasal blockages, bad tongue placement, probably other factors. My snoring improved a lot in adult years when I learned to keep my mouth closed and breath through my nose. My tongue position was so bad that an ent suggested tongue ablation, but instead I learned to deliberately thrust my tongue against my palate so it doesn't collapse back. It's difficult because in childhood I basically learned to mouth breathe because my nose was always blocked. That probably caused a lot of my problems with cavities and poor jaw growth. I was also bottle fed mushy foods for the first few years, instead of having more solid foods. I did use a night palatal expander as a kid, but wasn't too consistent in turning the key and my parents weren't really persistent with it.
They do, yes. There's a substantial body of research showing that soft diets lead to undersize jaws in a number of mammals, humans are just semi-unique in that our airways are very soft and floppy and it doesn't take much for collapse to start happening.
If you can't switch your diet to one that involves chewing for the sake of your kid, try and make chewing gum a regular snack.
