What happens when you don't have the cash to pay? Do we then see a whole new sector of predatory loans? Imprisonment? Increasing unpayable fines? None of those are good ideas, yet when things like this happen, our system has already fallen into these pitfalls. Witholding is an essential idea.
What would be nice is if we make the easy filing system but explicitly highlight the amount you paid in taxes compared to your income. Most people only judge on refund amount and rarely check the math on the exact taxes owed.