Once you checked in your hotel room in Italy, of course you have a (very) heavy luggage and you probably do not feel comfortable leaving it in the room, since you are in a foreign country and you don’t know how things work over there.
If you want to look like a real Italian citizen, forget about carrying a backpack, even a small one. You have to have basically nothing around a city, if you do not want to stand out as a tourist. Unless you are going on a day-long hiking trip somewhere, so you need to pack snacks & water, simply bring a purse and stick all the items you need in there, in order to be fashionable even if you carry map and camera. You will also have the impression to not feel that heavy, and you will definitely be ready for a day of sightseeing.
As far as it concerns men, do not be surprised to see some Italian men walking with bags. The ones whose size is something between the one of a briefcase and a purse. They can’t fit everything inside their pockets, plus it is seen as a very fashionable thing. As you know, in fact, Italians care a lot about how they look: they want to look great anytime, even if they simply go to the grocery. Keep in mind this, if you really want to look like them.
Italy is known to have so many robberies in the street and on the subway, but not in the hotels. So, feel comfortable and don’t think too much about who is going to steal your stuff in the room while you are having fun taking pictures to some monuments or visiting museums. Your stuff will be safe and you will be able to enjoy your day.