That's how it's been since... 2015 I think it was. When they started having Sunday Finals in the Arena part of Mandalay Bay and not the normal venue ballroom. I know guys who don't pay for the Sunday ticket and go hang out and watch what game they like on Twitch. Hell, there's always a number of dudes who treat it as an excuse to hang out and just play videogames in the hotel rooms more than anything else. If you're really invested in a game, you might luck out and get a game with low number of entries and so it'll have its finals on Saturday, making a Sunday ticket not necessary.