The Steam Machines PC gaming computers were pitched as a mighty alternative to Microsoft’s Windows when Valve announced them in January 2014. But when the company’s hardware partners announced their Steam Machines this week, only three of the original 14 vendors had products.

Since 2014, Valve has been working to create the SteamOS, the Steam Controller, and Steam Link products for computer makers to ship with their Steam Machines. So far, Alienware, Zotac, Maingear, and Cyberpower have unveiled gaming computers with the SteamOS. The SteamOS once seemed like some serious competition to Microsoft’s Windows monopoly, offering a Linux-flavored alternative to the OS that’s run PC gaming for decades. But at the start of this new era, it doesn’t look like it is turning out that way.

GamesBeat also heard why one additional company, Falcon Northwest, has decided not to ship a SteamOS machine as it originally planned. The computer maker had originally planned on shipping a version of its high-end Tiki game computer with the SteamOS this year. But because of some limitations of the SteamOS, it has decided not to ship this year. We sent a query to Valve and are awaiting a response.

“We met with Valve about our reservations concerning the limitations of SteamOS with high-end PC builds, and they agreed they were not issues that could be overcome in time for us to launch a Steam Machine this year,” said Kelt Reeves, president of Falcon Northwest in Medford, Oregon. “But they were genuinely interested in working to address them in future SteamOS builds. So the option for us to produce a Steam Machine is still open, and our Tiki PCs have been in production for years as Windows systems and are always ready. But for now, we’ve put our plans to offer a Steam Machine on hold.”

Reeves declined to go into specific reasons why. But we have heard that there are some technical challenges with the SteamOS, which is targeted at simpler machines where the number of options for expansion are limited. Right now, for instance, you can only use one graphics card with the SteamOS. And users also can’t use more than one hard disk drive in a system with the SteamOS. Valve is said to be working on adding support for more options, but that isn’t happening fast enough.

High-end PC maker Origin also said it is using Windows instead of the SteamOS in its Omega gaming PC.

Valve may be finding that it isn’t easy to take care of all of the technical problems that can come up in making an operating system for a gaming PC. On top of that, the original SteamOS was proposed when Windows 8 was the main competition. Now that Microsoft has shipped Windows 10 (to good reviews), there may be less need for an alternative.