It's not. The point of cash is to make you more psychologically aware of what you're spending so that you're less likely to buy something you don't need in the first place.

All of the online transaction tracking only helps with purchases that you've already made, so you can say "maybe I shouldn't have done that"...after the fact.

Cash based budgeting works beautifully, but it requires a change from what you're used to and there are certainly trade offs. If you're looking to save money though, cash budgeting is like magic.