So many kids are still wearing diapers past 3 and 5 years old now because disposable diapers are so easy to use and the diapers have become so good at keeping the kid dry that the kid does not feel wet in the diaper.
In the old days with cloth diapers the kid would feel wet and the cloth diapers required cleaning and work so parents were more glad to get the kid out of diapers.
But now with the disposable diapers it's easier to change a diaper instead of potty training the kid.
Some parents prefer to wait until the kid is ready which is a good thing as most kids will potty train on their own.
Some kids potty train by 3 years old and some not until 5 years old but eventually the kid will potty train.
However if they are 5 and still not wanting to use the toilet then you should force the idea as the kid will need to be potty trained to enter Kindergarten.
Diaper companies that make diapers for babies and toddlers are now making larger size diapers that can fit 7 and 8 year olds because some kids wet the bed and parents find the larger regular diapers better for kids who wet the bed than pull ups.
Also some kids are not being potty trained until age 5 or even after age 5 because some parents don't want to deal with the potty training.
Then there's some older kids above 5 that may have incontinence issues and need a diaper and adult diapers are too big while the toddler diapers in larger sizes such as size 7 will fit the kid better.
Then there's also some older kids that are autistic or has other disabilities that prevent potty training so they need diapers.
For kids who wet the bed most times pull ups leak and so the diaper is much better and keeps the kid and their bed and clothing dry.
Diaper companies see that there's a need for larger size diapers and parents are buying them so they make them and sell them.
I think it's good that diaper companies are making larger size diapers in their baby and toddler diaper line as they are better than most medical grade diapers.