Everything? Really?
I use hot air way more often than soldering iron when repairing something. When I'm building something my own, I use vapor phase oven, otherwise would use hot air.
I've never used a hot air gun for a QFN. They are a real pain to work with using a hot air gun.
Then please explain how you soldered center pad?
Why would anyone use a hot air gun for that? There are numerous methods for swapping out most big SMD parts with a soldering iron. Dave has videos on some of them.
Because it's much easier and faster. Chip quick is expensive and difficult to use, a lot of risk of damage. Also if you just use solder wick to remove it only once, without tinning and wicking again, you will get brittle solder joints after that. I'd use something like that only there is a high risk damaging something nearby by heating.
Most professional prototypes are hand soldered. Reflow is more of a production process. I assume from the tone of the OP's post that they are a hobbyist. I don't think they are looking for production solutions.
It's way easier to just use syringe with solder paste and hot air. Not to say soldering with iron only is not really applicable to QFN, LGA and most power mosfets.
I think its you who are out of date. In the 80s most people thought hot air was essential for everything SMD, and most labs had a number of high end (mostly Hakko) hot air tools.
Market is way bigger than ever before. And all of those tools by traditional companies are still made.
Look at Hakko's catalogue. They don't even make most of these tools any more, as the market isn't there.
Look yourself. FR-810B, FR-811, 851, FR-702