It depends greatly on the sector in Italy.
In construction I have seen more often than not the formula (jokingly) "180 days we'll see", meaning that for 6 months there is no way you'll get paid, then we'll see what we can do.
And the Law(s) do little about it (and no, these ones are not usually enforced).
But the issue is not actually the delay (for which - costly BTW - remedies exist) but rather the uncertainty and the time lost.
If we agree that you pay me after 60 or 90 or 180 days (talking of "continuous" work, supplies or services) it's ok, I can make a financial plan taking into account that delay, and include in my offer (at least part of ) the financial costs of that delay.
In the '80's and '90's I worked in a company that had "standard" payments terms for "large" suppliers set at 90 days, but then that actually meant that on the 90th day from the date of the invoice, a payment was made on the supplier bank account, always, sun, wind, rain or snow.
What happens often nowadays is that the agreement is actually 60 days, but after 60 days nothing happens, and so you have to call (and of course you can't ever find the right person) and then call again the day after, then you write an e-mail, then you wait, then you call again, then you write a letter and they tell you to have some patience as everything will be fixed next week, and next week you call again and there is a problem with the "system" (or with the bank's "system"), so you have a lawyer write a legal letter andm finally they pay with the 60 days becoming 90 or 120.
In the meantime you already delivered another supply, rinse and repeat.