>Of course it does - because both parents are responsible for the welfare of the children, and so if they both decide that they want to lower the standard of living that is a shared/joint agreement.
So a couple points here
1) we've now moved the goal posts, we went from the child needs the same standard of living, to now it is OK to lower it if both decide, to whatever extent that happens in dual custody situations.
2) except the oversight on child support recipients in most states is not that. The set judgement must be paid, and except for some usually minority line items the rest may be spent as the custodial pleases including the option of unilaterally allocating some stuff for stuff of no benefit to the child. As long as the child is not neglected or abused the custodial can unilaterally raise/lower the sol of child and put to themselves. So you are thinking of something else, it is mostly child support in name and is primarily a redistribution payment without oversight that it is all spent on raised qol of the child.
>Yes, sadly, having children means that sometimes you lack flexibility and can't make the decisions you would like to make.
It means they need necessities. It does not mean they need same qol in the event if divorce, except whoops we will move the goal posts as soon as you mention the double standard.