You might be in a country/region in which advertisers don't buy ads. But for quite some time now uBlock Origin isn't enough to block ads. Also if you are subbed/Twitch Prime to a streamer or have Twitch Turbo it might spare you a lot of ads too.
I have never paid a penny to Twitch, nor been given a gifted sub. So it's no that :) I know for sure my country has ads, as occasionally I load twitch app on my phone and it's unbearable.
There must be something different about how some of us are using uBlock Origin then - none o that applies to me, yet I only very rarely get ads for a day or so. I'm not even logged in to Twitch.
