Getting visibility within Steam itself is still probably the most effective way of increasing sales numbers - generally being featured/recommended within the platform is profoundly more effective than more organic marketing efforts (unless you really go viral on social media, for example).

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.