i think that why sponsorship works so well for youtube and podcasts is bc theyre pretty passive media; most people will just let a sponsored segment wash over them, they dont need to put anything into them. whereas comics demand a lot more participation from a reader, so if you had a sponsored segment in a comic, well... would you read that?
while it could be more simple a la buying adspace above or below the page, thats not as valuable to advertisers as yt sponsorship, especially when they can pay us less than pennies to have ads on tapas generally