Like for other measures, especially in the past few years, measures are taken and justified though a broad vague irrational paternalistic shout ("For the children"), and we are left with the unduly burden of trying to reconstruct the logic (if any plausible exists).
If you want to evade taxes by skimming 5 cents on each coffee, you have to sell 200.000 unregistered coffees to save 1.000 euros.
Which is more than 3 times what an average Italian bar sells every year.