With cash you spend less!

It is scientifically proven that using a credit card increases willingness to spend money. Therefor using cash makes you spend less and be more responsible with your money.

Governments and businesses would love you to spend more. See Banking to learn why.

Cash is easy to count

To spend less you need to know how much money you have. And for that you need to be able to count it quickly. With cash it is a relatively straight-forward process.

With a credit card you have maybe a rough idea. Since there is no way to know for sure. And swiping it is so easy that most of the time you don't even remember to count it in the first place.

Bank apps?

One way to see how much you have, would be to use a bank app, or a bank website. But those usually violate human rights with nightmarish terms of service and end user license agreements. The only way for them not to do that would be to develop them as Libre, but banks would probably not agree to this ( unless mandated by the state ).

And even with that, cash is still way more effective to keep you from spending compulsively.