PC gaming has kinda been a touchy subject in that it can become a very slippery slope. -Mainly because it would be a ridiculous task to catalog every computer and every computer component that was branded as a "gaming" product.
In regards to Steam Machines what's the criteria to be titled a Steam Machine? So far from what I understand the manufacturer just has to have SteamOS installed on it, and have a certain size factor. If that's the case we could be looking at practically an infinite amount of Steam Machines. If I were to set up a business tomorrow, I could start making and selling my own Steam Machines.
I can appreciate people wanting to show off their collection or even just wanted to list different models in the database, but I doubt too many people will be collecting Steam Machines. It's not [my] decision. That's just the way I see it.