It's a real shame that AIB partners aren't going after this market more. I'm sure I'm not the only person interested in a LP GTX950 or RX 460. What options do users of older (think Core2, LGA775/AM2, chipset IGP) PCs have for getting up-to-speed for modern web video decoding? Throwing working PCs into a landfill because they won't play Netflix HD adequately, shouldn't be the first option.
Most modern (> 2012) ITX cases I've seen are either "thin" which means you can't even add a GPU or have the capability to take a full height (minus the protruding heat-pipes some OEM's like to make), but half length card. The half height cards are being phased out (except in servers, but that's a whole other market). Hopefully with Thunderbolt 3 being more mainstream, we'll see more user-friendly and cheaper external GPU's casings.
Also, regarding your LGA775/AM2 comment, I think it'd be far more economical to upgrade the mobo/cpu/memory (Any Kaveri/Sandy* or newer combo is good enough atm) than buying a GTX 950 just for watching H264/H265/VP9 videos. Ironically, watching high bit-rate videos was a primary reason I moved from a C2D laptop to an Ivy-Bridge Thinkpad. Beyond sentimental (or compatibility) reasons, I'm not sure why you would bother keeping old hardware.
* I'd probably go with Kaveri/Haswell or newer