I'd like to know what the numbers are like for indie devs with their own twitch channel who constantly stream the development process, establishing a fan base throughout the year(s) of development before releasing on steam.
Being a game dev is akin to music, acting, whatever arts related.
It will cost blood, sweets and tears, full of ups and downs, and only an handful will manage to keep going at it their whole life.
Just like other arts, it doesn't mean people just give up, rather be aware it isn't just because they like playing on their games console every single day, that they will make it on the industry.
Discoverability and viewership numbers for game dev streamers on Twitch are really poor. Of course it can have value as a marketing initiative, but you can also grind that for months / years without seeing a significant effect on sales - the return on time investment is probably not great. Whereas getting onto the front page of Steam (as part of some seasonal event, for example) can do more for you in a single day than months/years of streaming or social media.
You're entirely correct about being featured/recommended, and there are ways to game the platform at your release to amplify these effects.
But my basic point stands; you can't just toss a game on Steam and expect good results.
Between the low barrier to entry on the store ($100) and engines like unity/gamemaker enabling basically anyone to have something to toss on the store, it's overflowing with shovelware. How many reskinned game engine tutorials alone are out there for sale as games? It's a complete mess.
I've been tempted to start streaming the development of my game on Twitch, but it's somewhat unnatural for me to do so (tried it a couple of times so far, been putting off doing it again for like four months now) ...but it also seems like one of the only ways to build an audience for your games ahead of time nowadays.