In a word: showmanship.
Apple makes its sales events (WWDC is a sales event) feel like something big, an occasion, something special to look forward to, like the revealing of a secret to the in-crowd.
This focus on the spectacle, the presentation and the perception, is a huge part of the company’s DNA.
People love this. Google is pretty terrible at it. Like Microsoft, they are getting better by watching Apple but showboating is not in Google’s DNA.
This isn’t just about Apple presentations. It’s all through the products and everything the company presents externally (internal tools are sometimes ugly and shit though).
Go back and look at the release of the original iMac; an outdated computer with a shoddy OS, built into a curvy, shiny, colorful case… people literally lined up to buy them. I refused on the grounds that I knew what was in that box… yet I still want one today. Mmmm shiny…
WWDC is the same. It’s not an accident. They think and work hard on making it happen.