This probably also has to do with the difficulty of trying to start a game off of Steam, promising Steam keys when the game is released, and then giving those keys out. Apparently devs can no longer do that.Steam keys have always been free for developers to give out or sell through other online or retail stores. That isn't changing. However, it is too easy for these keys to end up being used in ways that artificially inflate review scores.
An analysis of games across Steam shows that at least 160 titles have a substantially greater percentage of positive reviews by users that activated the product with a cd key, compared to customers that purchased the game directly on Steam. There are, of course, legitimate reasons why this could be true for a game: Some games have strong audiences off Steam, and some games have passionate early adopters or Kickstarter backers that are much more invested in the game.
But in many cases, the abuse is clear and obvious, such as duplicated and/or generated reviews in large batches, or reviews from accounts linked to the developer. In those cases, we've now taken action by banning the false reviews and will be ending business relationships with developers that continue violating our rules.
While helpful users in the community have been valuable in reporting instances of abuse, it's becoming increasingly difficult to detect when this is happening, which reviews from Steam Keys are legitimate, and which are artificially influenced.
I use the reviews there sparingly. I didn't realize (how could I) that so many of the positive reviews were generated by bogus dev keys. I am concerned about devs now basically being forced into early access for their alpha/beta because asking people to buy the game from their website with no promise of a Steam key is going to cut down that activity by quite a bit. As someone who bought both Rimworld and Factorio from the website, it'd be sad to have to buy the game again to get it on Steam.