Airbnb will build a new tech hub in Atlanta

OK I'll bite. Airbnb is a website. A hard-to-navigate, overproduced one, but it's still basically just a website coupled to a database. And it's not even as complex as Uber's because it doesn't need realtime GPS tracking of anything.

Why does Airbnb need a "tech hub?"

Maybe they don't "need" one, but they have contributed in a very meaningful way to the web dev community so I feel that this is a harsh take. Check out Lottie, Mavericks, and their contributions to the React ecosystem.

You're asking the wrong guy; I consider React one of the worst mistakes in technology, and it's the main reason Airbnb's website sucks (I speak as a superhost who has to use the thing a lot).