Paragraph by paragraph:
Steambox would give you that option. Consoles don't.
So you'd rather buy two devices at a minimum of $400 a piece (but likely way more) than move a single device that does the job of both? And you think that buying one locked down PC like product and one open one is a good idea??? (Paragraph 2 and 3)
The idea is one less PC, actually.
I regularly use my PC in the living room. And regardless, the Steambox would let me use whatever I want wherever I want so I'd just switch between interfaces as I wanted.
The last two paragraphs perfectly describe what the Steambox is. Except for playing console games, of course that is because MS and Sony won't allow it.
The Steambox is for console gamers, not PC gamers, as should be perfectly obvious. Specifically, it is to get them adjusted to PC gaming so consoles can be destroyed. For you to not want Steambox because you already have a PC isn't an argument against Steambox... you already have one.