This.

YouTube and Twitch are in this same boat. The video format is a hugely lucrative one. Many people consume it passively, either in the background or while doing other things. The ad exposure is huge, and there's a ton of value in having people invested in your platform, so financial incentives are high.

There just aren't enough people who are willing or able to put that much effort into making rich content for free, especia6when there's a payed alternative