By the time the bottom of the crust is golden brown and crispy, the cheese would be burnt if you put it in all at once. Alternatively, you end up with a soggy crust but perfect cheese.
So instead you crisp up the bottom first, and then get the cheese and toppings melted.
Does anyone else just get the urge to maim themselves sometimes?
Sometimes I think "I should lose an eye" or "I should chop off my thumbs" and I don't understand why.