A social worker once told me that modern, sophisticated, disposable nappies, are the reason for some children not being adequately potty trained before school.
We once used terry towelling nappies - so many mums couldn't wait to potty train their children in order to get them out of those horrible things. I know I hated having to scrape the towelling nappies clean before dumping them in a lidded bucket of water, with "Napisan" sterilizing powder added. And washing and drying dozens of them every week wasn't always easy either.
The modern disposable nappies are so efficient in catching urine and keeping the child comfortable and dry, that the child has no incentive to get out of these nappies or pull-ups themselves. And I think it also makes it easy for some of us to put off the stress to ourselves and to the child, of the potty training regime. (Which, depending on the individual child, doesn't always go smoothly.)
The very comfortable pull-ups that children can wear at night, also encourage mums to put off attempting night-time potty training. Which I remember as being very stressful - having to get up at night to change the bedding after the occasional accident. Especially as in many households today, mums and dads are both working.
I think what must be happening is that now children start school at 4, time suddenly runs out for some busy (or lazy - dare I say??) parents to begin or complete the potty training. Which is why, I think, some are not ready to come out of nappies or pull-ups before actually starting school.
I feel very sorry for the teachers -and the children, because the children must feel humiliated if some of their peer group are already dry.
I know my children hated their sodden terry towelling nappies - which once wet, would hang heavily and scratchily between their little legs! So they were proud and happy to learn how to get out of the beastly things!!