The big advantage of cash envelopes is that, if you budget properly, you will always have the cash to pay a bill when it comes due. No more worrying about where the money will come from, be it for mortgage or rent, utilities, car payments, repairs, taxes, discretionary spending, etc.
Second, and more importantly, this method doesn't provide any real guidance on what to do with money as it comes in. You're left to try to figure it out as you go. Mistakes are made...frustration sets it... you give up. That's because your budgeting worksheets are missing the most crucial part of any budget _ the spending plan.