It's not weird at all, it feeds into what you just said.

I think it is a pretty obvious indicator that steam caters to a small market. The steam crowd is the core gamers on PC. The sudden shrinking in the PC market has been well documented as being caused by smartphone/tablet sales. The tablet/smartphone systems aren't replacing high end PC's obviously, they are the new devices for the casual crowd. Newell should know this, that is why he wants to run to Linux. Who supports Linux? The build your own system group=very small in comparison.

I see a bright future for Steam!

Well you know how it is.  That's just the hype pushed by the tablet/smartphone market... pushed along by the media because the narrative of a shrinking home PC market is more likely to get hits/be intresting.

Hence why the theory won't die.

I mean hell, i'd look at home phones.  Which while are declining in marketshare are barely doing so... and actually hold zero advantages over cellphones.   Unlike Desktops which hold huge advantages over tablets and laptops.

This was already discussed overhere...
http://gamrconnect.vgchartz.com/thread.php?id=168628&page=1#

My take: Gabe is a wise man who is doing and saying what he must in order to keep his business afloat. iOS app store, Android app store and now Windows app store are proprietary platforms and they all sell games, and while they are not in direct competition with Steam yet, they will get there in a few years when hardware gets more powerful. In 5 years when Android, iOS and Windows products are present on desktop, mobile and living room (as consoles), providing cross platform entertainment, Steam, as another proprietary platform, will be in big trouble. Hence Gabe is preparing to make Linux the "Steam" platform, since no one else is rushing to support it.

Otherwise Gabe is totally barking up the wrong tree and factually wrong with this "PC sales down, Steam usage up" argument... Latest stats indicate that almost 15% of steam users are using Windows 8 and over 95% are using Windows, while under 3% are using Mac and less than 1% are using Linux. Windows is driving 95% of the Steam adoption while its also shrinking in sales apparently.

This. People that don't replace their old PCs still use them anyway. The same applies to consoles, BTW, before my sister bought her PC she still used her old Gameboy and our really old Intellivision, every now and then. I too used it for years after its generation ended, until I switched to ZX Spectrum first and finally to PC. In these 16 years of owning a PC I just did three major upgrades after the initial purchase, although I did a lot more minor updates. And when I did my last major upgrade, I used the newest spare old parts to build a PC for my mom, that worked for some time, then I had to change its mobo, CPU and RAM, but I recicled again all the rest, including the case for the 3rd time.
PCs are just like those damn zombies in Thief I, very hard to kill.   

Linux ? LMAO