Got to the airport really stupidly early once and stayed there all night, because I was travelling with two people who also couldn't drive. One's dad was going to drive us but injured himself so we took a train over there 8 hours earlier than we would have.

Tl;DR trains make people do long visits at station.

And weirdly there were a lot of other passengers entering the airport at 6AM or sooner and they were having a great time wasting their money on everything.

But also I presume the pizza comes already made and kept warm or something. If not, then some authentic Italian pizzas, the basic topping, softer and chewy ones, can take just 6-12 minutes to cook. People have time to sit down at cafes and restaurants sometimes :). Maybe only the USA has the speedy aeroplane infrastructure you're used to