Pizza - why high temperature?
it is commonly suggested to use as high a temperature as possible when making pizza, sometimes the traditional wood-fired brick ovens of pizzerias, reaching 600 F or more, are mentioned. But how, exactly, does temperature affect the pizza, and why are higher temps better? E.g., why is 3 minutes at 600F different than, say, 15 minutes at 500F, or 25 minutes at 400F (just guessing cooking times here, for illustrations).
And what are the limits, theoretically? Would a few seconds at a couple of thousands degrees work? Or some milliseconds or microseconds at a million degrees?
I can't be of much help to you about the hows and whys, but I can recommend that you google search Heston Blumenthal In Search of Perfection Pizza - he researches the whole process and covers many of the questions you've posted here.
Me think (after less than 10 secs. of thinking about it)
The only thing really needing cooking in a pizza is the dough; you want to cook it as fast as possible without over-cooking the other ingredients.
To get the crispy crust. Lower temp would work but then you get a soft crust. A million degrees and you'd liquefy it. I bake focaccia pizza at 350ish because it's not a thin crispy crusty chewy pizza.
The longer bread is subjected to heat, the drier it gets. That doesn't stop every corner pizzeria from cooking their pizzas for 10-14 minutes, and all of the leftover crust in the box is the proof that it's not good.
The best reasons for high heat when cooking pizza are well described here so I will only add that some brick ovens reach well over 1000 degrees at various points and it is not uncommon for some bakers to prepare a pizza in ovens reaching 800 or 900 degrees.