We have that, and it's called "installing from the developer's website".
Allowing everyone on Steam would be a mistake; driving down the minimum quality of games makes it harder to discover and reward the best games. Steam's success so far has been in quality and discounts.
Gaming critic Jim Stirling has a youtube channel dedicated to this, e.g. Air Control (https://www.youtube.com/watch?v=VYArgbWVtGc) was a famous example. Day One: Garry's incident (https://www.youtube.com/watch?v=KjTa_x3rbJE) was another trainwreck which got famous because the dev filed false DMCA claims to take down negative Youtube videos.
Both of these and many more were on steam for $30 or so
They are working in steps towards this. The last discovery update addresses a lot of the problems they had with discoverability and also focuses on rewarding better games more than subpar ones.
The reason behind showing metacritic score, user reviews, and curator reviews, along with introducing a discovery system that considers the quality of the games it suggests, and pushing some of the approval process onto the users (greenlight), has been all to try and decrease Valve's position as an authority on game quality.
There are some horrifyingly poor games on steam already, most of which get removed after a bunch of people complain about it either a) being a scam, or b) being literally unplayable, after which no refunds are given and the game is removed from the store.
But bad games, who make truthful claims, are fine, and that is intended
> "One of the worst characteristics of the current Steam system is that we've become a bottleneck. There's so much content coming at us that we just don't have enough time to turn the crank on the production process of getting something up on Steam. So whether we want to or not, we're creating artificial shelf space scarcity.
> "So the right way to do that is to make Steam essentially a network API that anyone can call. Now, this is separate from issues about viruses and malware. But essentially, it's like, anyone can use Steam as a sort of a distribution and replication mechanism.
> "It's the consumers who will draw it through. It's not us making a decision about what should or shouldn't be available. It's just, you want to use this distribution facility? It's there. And customers decide which things actually end up being pulled through. So Steam should stop being a curated process and start becoming a networking API."
http://www.gamasutra.com/view/news/186168/Gabe_Newells_visio...