Honestly, this doesn't surprise me.
At the end of day, for as much money that comes in to Twitch, their prices (& their reluctance to give partners or really ANYONE creator passes) plus the lack of really getting anything worthwhile in return... why WOULD someone want to go?
Twitchcon appears to be giving away hundreds (thousands?) of 3-day tickets, likely because of low sales.
Ambassadors, brands, artists, and other attendees are being given codes for free tickets.
Current publicly available data suggests sales are 33% below last year.