You're not missing anything... It's not a rare beer fest at all, not sure why you'd think a big fest needs to have a bunch of rare or hard to find beer pouring.
Look at the GABF... it's usual offerings by usual breweries, it's nothing "Special". Us as oregonians do not get many chances to gather outside very often as the weather is somewhat... fun... haha.
With that being said, there are either breweries that do not make their way to oregon often if ever at all, or breweries that do distro here with a few minimal options bring out their beer is also fun
- Lost abbey has been here previously, we never see them
- Dogfish head brought in some of their beer we do not get over here
- Terminal gravity, who is in oregon, but only really has 3 beers they distro brought in a lager
- Logsdon Farmhouse Ales brought in beer that doesn't make it into distro
- Sprecher Brewery brought beer
- etc etc
Plus, it takes place outside on our waterfront, next to a river smack dab in the middle of town.
Also, downtown partially closes for the march that takes place during the opening festival
Why wouldn't you want to drink "easy to get beer" with views like this?