Because most video game publishers allow them to stream without paying. But not all: https://www.theverge.com/2018/11/28/18117172/nintendo-youtube-monetization-

Because most video game publishers allow them to stream without paying. But not all: https://www.theverge.com/2018/11/28/18117172/nintendo-youtube-monetization-partner-program-super-smash-bros-ultimate-lets-play-livestream https://www.theverge.com/2018/11/28/18117172/nintendo-youtub...