Lots of four year olds won't have a diagnosis yet. Things like autism, dyslexia, dyspraxia, hypermobility, ADHD, won't have been diagnosed if not severe.
Cost of living crisis can account for other things. Going back years to 2000s
Living in the innerciity/poor estate ...one of our local parks is known locally as dog poo park. Another was broken equipment and glass scattered across the playground. Another local city park known for grooming, a murder, a serious assault, in the red light district...cash strapped councils aren't maintaining parks. A shit environment getting kids down 16 flights of piss soaked stairs as the lift is broken.. Getting two kids and a buggy down stairs is a lot more difficult than loading up your kids into a car parked on the drive. Environment has a major effect. As does housing.
Parents working all hours and not being home much in the evening to do more than the basics. (Rents, house prices requiring two parents to work now)
COVID accounting for other stuff.
Being poor/hungry is fucking miserable. If you are using up all your energy on just getting by there is not a lot left for other stuff.
Parents poor health..(maybe going back to the previous generations parenting /economic circumstances)
People moving around a lot as rented housing is insecure.
Access to food. Ex used to live a long walk away from a supermarket. There are loads of places that don't have good cheap food provision.
Libraries are closing.
Bus fares are rising.You can't get out of area to places.
Look at why parents aren't preparing kids for school rather than calling them lazy.
People raising kids in HMO where the only outdoor space is the front parking space or road.
If you live somewhere where people light fireworks in the street...or there are boy racers, or there are gangs and knife crime..