We should not be recommending Nvidia. This page is not about "hardware that can work", but about "hardware that is recommended to buy". Nvidia is not flawless, and just over all not well integrated. Think about a user that has no experience with Linux, maybe not even experience with computers. With an AMD GPU, everything will work after installing the system. With Nvidia there is lots of jank. This gets even more important with SteamOS, which might not even be possible to use with an Nvidia GPU (immutable file system + licensing issues).