Why can't you have a cappuccino after 12 in Italy?

Excuse me, I've heard that there's a strange rule in Italy about not having a cappuccino after a certain time. Could you please elaborate on why one can't enjoy a cappuccino past 12 PM? Is it a cultural norm or does it have something to do with the coffee itself? I'm genuinely curious to know the reasoning behind this tradition, if any. Is there a specific penalty or is it more of a social taboo? Thank you for your time.