Furthermore, even when social mobility is easier, it still takes time. You can work as hard as you like, and it still won't happen overnight. So essentially, you're proposing to punish people simply for being poor, even if they're working hard to improve their situation.
People are having fewer children than ever. And while I agree loopholes need to be closed as much as possible, what would you propose we do about those who slip through? Punish their children by denying them medical care? What did the children do wrong?