If you're already AT the building to take the pizza away, why not just eat it while it's hot?
It takes about 2 to 4 minutes to eat a pizza, but if you wander off with it, it becomes cold, the cheese congeals and you're more likely to just have all the toppings slide off so you're left with a limp piece of bread with a trace amount of sauce on it.
If you have it for delivery, then you have a trained specialist that has a special thermal insulator that can keep the pizza hot until it gets to you.
Why would you settle for cold and unpleasant pizza when you could just have fresh pizza?
Most people have these things called "friends" or "family" that they're taking the pizza to and sharing it with them. Also, if you've ever set foot in a grocery store, you'd know large insulated bags are pretty easy to come by.