Because the police don't frisk down businesses and factories, and the laws are not... they don't CARE to actually enforce them. They want to bust a person walking down the street with a knife, for the IDEA that that person might have something they could use to defend themself.
They don't actually care to go after business, even if it's illegal, because the law is a farce. In the USA, when we say it's illegal to manufacture machine guns... we don't just bust you for having an auto switch on your Glock when a cop sees it, and then let the businesses alone. Colt can't just start making autos and send them to a country that isn't so strict about autos, the way Italy freely makes automatics and Lionsteel isn't worried. Nobody is coming to enforce a knife law over at a knife factory. Boker may do it in a strictly-speaking legal way, I don't know, just to look on the up-and-up, "Our company complies with laws, we are not lawbreakers!", some people are very offended at the idea of breaking a law, no matter how stupid or ridiculous or not "real".
Technically, they can't say "A stiletto may NEVER exist in Italy, because, what about museums, what about a potential SF unit," not that those guys usually always need autos, but in theory... So, by the permit thing, it's not like you can go and get a permit for an auto as a civilian. It's to make it illegal. It's so that, in theory, if you had a historical stiletto belonging to, idk, Vito Corleone's grandfather, you could keep it for display in your museum, or if you are a tactical operator for the French SWAT team, you could have one.
What I'm saying is, I don't think the laws are truly that strict about businesses and manufacturers, as Balisongs and autos are a felony here in CA and you can get one in any crappy pawn shop, swap meet, mall shop, stand, whatever... they don't check the knives before they come into the peanut stand, I guess. So, you could probably get one like that in Italy, too, but the law is moreso there so that they can bust you if they find it on you and they don't like it. It's not a "serious, enforced" law, it's just there to fk over the average dude.