I think this technique varies in success depending on the content of the video. And for some people even just being satisfied enough with their own drawings is too distracting or time consuming compared to less diverse stock footage options. They may be self conscious about their skills as an artist or worried that their drawing isn’t really expressing their point as well as stock footage might have.

Even just whipping up some stick people in paint, saving the frames, and ordering them in the video can be more time consuming than picking some clips from an existing library of footage. Many youtubers still have full time jobs and may not have the time or creative energy to add their own drawings to a video.