In order to make videos, I heavily rely on viewer donations.
Why don’t you use ads?
I do use ads! However, they are not a very reliable source of income. I also upload videos to Vimeo, and they don’t play advertisements on videos. (Although, the benefit to this is that I don’t have to worry about an apocalypse type scenario happening on Vimeo! Plus, Vimeo also provides my videos at much higher quality than YouTube does.)