- Complete access to Apple engineers, who will be blunt with you and share details that are otherwise not public. I worked on a couple things with engineers from the labs, and it was refreshing to get answers like "Yep, this is a serious bug, but it touches too many things in the system, so we'll fix it in the next major release."
Also, it's interesting to get to see what the engineers see on any given radar ticket I filed. Whereas several looked dormant on my end, a couple had rather heated discussions.
- Networking/rubbing shoulders with great developers from the community.
- You get information about upcoming features in upcoming products. Sure, places like Ars Technica or the Verge will cover some of the sexier things lightly, but there's still plenty of in-depth technical stuff that aren't understandable by your average tech journalist.
Some of the early Grand Central Dispatch and ZFS comes to mind. Those presentations were essentially given in ObjC, so if you weren't familiar with ObjC, you couldnt really get the point of what they were about.
That's the main reason. You can talk to the guys who MADE your system and have THEM describe and discuss things with you.
(Disclosure: I read that on the internet)
2. Connect with Apple employees and ask questions
3. Attend other side events like hackathons, meetups, etc...
4. Potential opportunities
5. There is a difference between attending in person vs watching stuff streaming off your monitor from afar similar to watching a sports event on TV or in-person.
Not all of the above are reasons for why I go to a conference but I'd imagine that some of those points apply for others (and probably stuff I'm not listing here at the moment).
Long answer: Conferences were traditionally the way to get the latest information on technology, but now that we're so well connected, that's no longer the case. As with all relics, people will continue to do these out of industry habit, and for the networking opportunities.
I'm so glad the years of bidding on wwdc dvds on ebay is behind us.