As someone who was gaming since the 90s I didn't understand streaming or long plays in the beginning but now I really appreciate long plays as they allow me to scratch an itch without getting too engrossed in a game. I find it a lot easier to pick up and put down a long play of a RPG than invest 30+ hours of time and thought into playing it.

For mechanistically intensive games it can be enjoying to watch masters play at a high level. Watching people win 1vs3 in Elden Ring or people do high level play in Monster Hunter or Devil May Cry is satisfying for someone who knows enough to appreciate the skill without having the time/desire in mastering frame specific inputs (I prefer directing that degree of focus to learning an instrument out of personal preference)

I initially discovered game streams because I find them perfect for falling asleep to lol