First, don’t expect your pizza to be pre-sliced in Italy. Unless you’re going to rip it apart, you’ll need to get out the knife and fork to cut your slice. Sometimes from there you can pick it up and fold it. Most Roman pizzas tend to be a thin crust, almost like a cracker, and good for this method.
In Napoli (see our visit here), you eat the entire pizza with a knife and fork (check out our favorite book on Napoli here--a great read). There’s really no picking up a slice. It’s just how everyone does it. It’s the culture. When we go to restaurants in the United States who claim to make Neapolitan-style pizzas, we appreciate it when we don’t have to request the pizza to not be pre-sliced. I get that it's American culture, but if I’m eating a Neapolitan-style pizza, I want to eat it in the Neapolitan style.