It depends on what it covers and how much you're paying. If it's one of those basic packages the airlines offer at checkout, they're often overpriced and cover barely anything - like massive delays or cancellations you'd be covered for anyway under EU regulations. For short routes like Milan-Rome honestly I wouldn't even worry about it, the risk is low. If you really want to protect yourself, a generic external insurance costs less and covers more, but honestly for a domestic Italian flight I think it's pretty much pointless unless you're traveling sick or have some special situation.