And if tax withholding laws changed to err on the side of under-withholding for poor people, those people would disproportionately fail to be able to pay their taxes when the time comes.
Most people can't budget, poor people especially so (it's among the biggest and most likely reasons why they are poor). They see money, they spend it all immediately. Saving? Investing? "roflmao" or "I can't.", they will say. The only way to address this so certain, specific, important payments are made absolutely is to literally take and keep the money out of the person's hands until the payment is made.
When income is 80% of the minimal bills, which dollars are the fun ones?
> But anyone who has actually dealt with poor people who live paycheck to paycheck knows they are not good at budgeting and planning.
You may not know that assertion is uneducated nonsense. The nonsensical part is the inference that better budgeting is all that stands between 80% of minimal bills and 105%.
Past that, an extended time in hunger-level poverty tends to lead to some hyper-focused money management. As in being intimately aware of each penny that hopefully will add up to this weeks bag of white rice.
Not sure I'm explaining that properly, but it was the sort of math I encountered dealing with such individuals.
There is also a general pattern of spending "extra" money on things like parties, experiences, consumables, etc. Better to spend the money on a pizza party and gocart trip for their kids than to stash it away in a savings account. Better to spend the money on beer for a party than even to hide it under their mattress.
> they get a big paycheck once a year to pay off whatever
If you have something big to pay off, you usually need to do it right away. You probably can't afford to wait however many months until you get your refund.