How do you know the Steam hardware survey gives an accurate representation of the PC, or even just Steam, community?
You don't need a huge percentage of steam users participating in the survey to get an accurate representation.
Also the average steam using pc gamer has a better pc than the average non steam using pc gamer. WoW and LoL are the most popular non steam games and have very low reqs.
But you need to take a representative sample
"Also the average steam using pc gamer has a better pc than the average non steam using pc gamer."
Please, show me your data
If valve isn't getting enough respondents for an accurate survey they will simply keep sending survey requests until they get enough. Google survey calculators to see how small a percentage is needed for an accurate survey.
Steam is required for many multiplats. Multiplat average min req is much higher than LoL, WoW and just about any highly played non steam game. The only popular non steam games with high reqs are BF 3,4 and common sense would dictate most BF players use steam.