There is a very similar situation in Germany. The reason behind this is that you can use older POS systems for tax fraud (I never fully understood the details), which apparently was quite a thing amongst smaller businesses. The tax authorities then demanded a perfect chain of paper records (apparently the paper recipe contains some kind of a reference to earlier transactions). Bizarrely, they actually asked customers to keep these receipts which pretty much no one really did, but it was a public topic for a couple of weeks.

German source:

https://www.bundesfinanzministerium.de/Content/DE/FAQ/2020-0...

In Italy, that’s law because there used to be/is (don’t know which is true) a culture where, some/many cafes and restaurants let some/many visitors pay ‘under the table’, dodging VAT taxes.

That law requires shipowners to give a receipt and customers to keep it. Customers can be fined if, a few meters outside the shop, a policeman asks them to show their receipt, and the policeman has evidence they bought something or some service (https://www.accountingbolla.com/blog/sales-tax-in-italy-iva)

I’m not really familiar with the matter but this year they started requiring immediate reporting from the POS as far as I know. That should tell you how serious they are about receipts in Italy (because there is/was widespread fraud.)

It's the law