That's already how it is among the SC2 twitch streamer community (and no doubt true for BW and other games with small but dedicated audiences).
Mid-tier streamers get the majority of their money from direct donations (which display a notification live on stream) and twitch 'subscriptions' the viewers buy for $5, split roughly 50/50 between streamer and twitch (usually to unlock access to their VoDs or other perks). Which really isn't the same as passive ad revenue from the platform, as users aren't exactly incentivized to give this money directly to twitch.
The successful ones actively solicit or otherwise encourage subs and donations, and those who struggle with this have generally moved on from the platform or away from streaming as a career. Many of them also have patreon for extra perks, plus a youtube channel with a more curated selection of videos (which I've heard pays better for the time investment, since the content is mostly already created for twitch streaming or sometimes other sources).
At this moment I'm watching a guy whose monetization strategy is a roulette wheel program with challenges and dumb stuff for him to do that gets rolled whenever a viewer donates above a certain threshold. As I am posting a viewer literally just hit "play 100 games" (obviously very low percentage roll, first time I've seen it) and the streamer is pleading with chat for them to let him play the 100 games over the weekend instead of right now. Pretty entertaining, and a funny coincidence to illustrate my point as I'm typing this.
Another guy who is a caster (like a sports announcer for e-sports tournaments) hosts tournaments via donations, ie every donation has a portion go to the prizepool and tournament costs. He has relationships with all the top pro-gamers in the scene and gets great line-ups for relatively small offered prizepools by being a community figure and also being a great organizer and scheduler, etc to accommodate the pro players to make it effortless for them to participate.
It's been this way for many years for streamers trying to make a living with 1-2k average viewers and below, typically working 40ish hours per week if I had to guess (not counting practice and any professional obligations with e-sports, sponsors, etc).
Anyway, I love professional SC2 even though I haven't played for years, and I spend way too much time on twitch.