You can hang out with people outside the convention. If a convention doesn’t have actual things TO DO, I’ll either lobbycon, or not attend at all. That even goes for PAX or MAGFest as well. A convention needs to give you a reason to be inside. What does your badge get you that you can’t get if you are stuck outside? Blizzcon is not like other good conventions that have things to do. It’s like PAX, but it’s not even just the Expo Hall (like E3). It’s just one booth in the Expo Hall, and that’s it.
Also, you can buy the same worthless merch online.
A sporting event is worth attending in person. I paid a lot go to a hockey game last night. How is an announcement worth attending in person? Nobody pays to attend sports teams press conferences in person, nor would they. We let reporters attend and just read the news later. Imagine if teams started having their press conferences in the arena and charged for admission! It would be a laughing stock.
Concerts and cosplay contest are good. But unless you are in the cosplay contest, I guess you can just watch it online. Same for the panels. Unlike other conventions Blizzcon streams EVERYTHING. You just buy that virtual ticket and stay at home.