itch.io is a D.I.Y. game distribution service that was launched in 2013 where just about anyone can create and upload a game, sell it, or make it available for free. Its focus has been on finding and distributing smaller more experimental indie games, functioning much like a D.I.Y. record label for video games. Recently, its client software cropped up on Valve's Greenlight service where it was hosted for twelve days before Valve removed it. Valve commented on the removal in a statement sent to Leaf Corcoran saying “The reality is that we’re finding that we just don’t have the tools and processes to handle many types of non-gaming software very well right now. We’d like to accept more kinds of software on Steam, but right now we need to focus on a smaller scope until we have better tools and processes in place." Valve has yet to issue a public statement on the matter so this is all we have to go on at this time.
Develop points out that Valve currently has non-gaming software available on Steam. They are mostly game creation tools including art and modeling tools, animation software, design programs and even some video production tools. In the time itch.io was on Greenlight, it received roughly 3,000 yes votes and reached the number four spot on the service. They also have games that link with other distribution services such as Ubisoft games linking to Uplay, but they don't distribute Uplay itself on their storefront.
While itch.io may have had the most noble of intentions with this endeavor, it seems silly at best and downright stupid at worst to think that Steam would allow a digital game distribution service onto their own digital game distribution service. Not only are the logistics of that mind-boggling but what company would ever distribute a competing service on their own service? C'mon son.