I don't watch a lot of Twitch, but they have adverts imbedded at server side. I run an ad blocker (uBlock Origin) on my browser and I have to sit through the adverts before getting to watch a stream.
For YouTube (Google) I think it makes sense for them trying to force the adverts onto users, they want to maximise their revenue. My workaround is to sign up to YouTube Premium through a country that has it a lot cheaper (in my case Ukraine). I don't mind paying YouTube £2 a month, as I watch it a LOT. I object to the £12 a month they would officially charge UK residents.