Aside from love handles and heart disease, there's really only one discernable problem with pizza: you cannot instantly summon pizza wherever you are on this planet.
Yes, it is categorically true that if you are somewhere indoors in the United States, you can probably finagle some type of pizza delivery to your location. After all, pizza delivery has (probably) existed in perpetuity since 19th-century Italy, and it's one of the most regularly ordered foods in the United States. But alas, occasionally the need for pizza arises in the great outdoors. Friends tend to gather at parks, beaches, street corners, national monuments, and other points of interest out in the wild. And pizza is by nature a communal food, meant to be shared with friends, frenemies, and good-natured strangers. Do you see the disconnect here? It's only natural to feel the pull of pizza in confines of nature.