I just don't think it's a reality that should happen when it could be split down the middle.
Splitting the kids expenses right down the middle may seem like a good way of ensuring that the ex is making a fair contribution

but then the problem would be that the maintenance money could not go on things such as rent and food bills or petrol or car rego or insurance...

the way it is now is that the primary carer can determine where the money will be spent which is really the best option because needs may change from month to month.