Who has the time? We're all grinding to make money. Occasionally I play some online games with friends, but you'd be surprised how many times some of them can't make it because they're working OT to cover child support.
Running errands together means socializing and doing chores at the same time. Anecdotally, I have seen that arrangements among some wen I know - even cleaning one of their house together and next week another house. Mutual help in boring works and socialization at the same time.
Most places calculate it as a percentage of earnings with some other factors included at a single point in time (resetting takes other petitons and seems to rarely happen). But that percentage is translated into a dollar amount and is basically set in stone from that point on. Lost your job? Tough shit, keep paying while you look for a new one.
Now imagine you're deployed and earning hazard pay when they set that initial dollar amount. Then a couple years later you're not earning that same pay because you're in the reserves. Now you have to work OT at your civilian job to make the payments and support yourself because the way the courts handle child support is ridiculous.
You can petition for reevaluation every 3 years. Changing support obligations is not that hard. Changing custody is.
Your scenario is equally real for salespeople. Income is imputed based on last 3 years' earnings. If you get laid off and your spouse abandons you, you're expected to continue paying out based on your peak earnings. If the last few years were good to you, your next few will be hell.
It's not a good system but there aren't really any solutions that can't be gamed by the men.
"You can petition for reevaluation every 3 years."
Yeah, but it's basically at the whim of the judge. As you mentioned the gaming part, it seems they tend to be biased against many adjustments by thinking it's being gamed.
It's absolutely ridiculous to think this is a good system though. In my mind, you're better off letting some gaming occur than to force people into impossible positions. Not to mention, the current system does nothing to curtail the gaming done by the lower income spouse, women who have multiple children from different partners, or true cost of raising the child vs what someone gets.