Baby diapers are so thin now as research and design has found ways to increase the absorbency of the diapers while making them thin.
In the early days of disposable baby diapers they were thick and had to be to absorb the pee but now they've found ways to reduce the thickness of the baby diapers but still have them absorb a lot of pee.
Parents have also wanted thinner diapers that were not so bulky that could be hidden under the baby or toddlers clothing.
Although we know that babies and most toddlers wear diapers and need them some parents don't like the look of diapers on their baby or toddler and would rather have them be as thin and discrete as possible.
In the old days disposable baby diapers use to be so thick that the toddler would waddle and their legs would be spread apart.
The diapers would also sometimes crinkle as the toddler walked or the baby crawled.
Now though diapers are so thin and cloth backed that they don't make much if any noise when the baby crawls or the toddler walks.
Thinner disposable baby diapers also means more diapers can be shipped in the same box or pack and take up less space which increases profits for the diaper companies.
The thinner diapers also make it easier for toddlers to walk as well.