Plenty of musicians, artists perform/create with no prospect of monetary gain. They do it for the accolades. They do it for the positive feedback. They do it because they have to: they're artists.
I suspect YouTubers like "Applied Science" are artists of a sort. I guess I'm drawn to YouTube artists.
Applied Science is a good example of someone who has not gone the sponsor route. He is crowd funded and has a Patreon page that is setup to charge when he releases a video(I'm a patron of his actually). It is still work to make the videos and describe what he's doing and how it works. He could be sponsored, even relevantly, if for example he used a Rigol scope to show something and then talked about it for a bit. But that wouldn't mean he is any less passionate about what he is doing.
The musicians and artists example is different though. Their hobbies produce media as an end result. Publishing it is part of the process. I make videos about vintage computers. My hobby without youtube would just be me sitting alone in a room tinkering. Creating a video out of whatever I'm doing requires deliberate additional effort.
Gessoing a canvas is work. Setting up, taking down a drum kit is work too. If you want the world to see your hobby, or your art, there is a cost involved. We accept that cost for exposure in return: for the joy of sharing in return.
I don't fault anyone wanting to make money from their hobby or their art. But I also respect a little more perhaps those, like Applied Science, that don't want to ... sully their art with a blatant sponsor plug.
Again though, I'm just a viewer, fan, enthusiast, lurker — the content creators get to make their own rules, I don't get to tell them how to run their channel.
Subscribed to your YT channel, BTW. Wrote a very early game on the Commodore PET, LOL.