Valve would never sell fake digital goods. Hats? Gun paint jobs? Nahhhh that's beneath them. I mean worse still, NFTs can be traded on the secondary market, which would be completely ridiculous for a company to allow for cosmetics in a video game of all things.
I'd say Gabe don't want to spent Valve's good guy points in anything controversial.
The reason why big publishers like Capcom and Square Enix, freely publish on Steam (without need for bribe money like Sony, Microsoft and Epic do) is due to the attraction of the "good guy reliability".
For example, during Bethesda+Valve pay mod fiasco Valve was quick to share half of the guilt with Bethesda and shut down everything... while of course, Bethesda show they were (and are) all the way in with the concept.