Although Steam is an off-market company, they still need to make deals with on-market companies, not surprising run by a bunch of lawyers.
I doubt Gabe or his team actually cares (there are legitimate reasons for VPNs after all, off on a rig in a location that doesnt allow it, etc etc). but in the end they still need to sign off on deals which usually come with booksize amounts of paperwork and agreements.
Technically they could just falsely ban fake accounts/cheating accounts and blame it on them, job done.
Even if you buy it from Russia, Steam still gets a percentage, not the biggest, but they I doubt they would mind, its not like millions of people bother.
Why we don't just consolidate Ratings agencies and all this turd into one group is beyond me, there should BE NO BLOODY REASON for this crap today in this globalised world.
Same with TV and Movies, I know its a silly position but I cannot be ass'd waiting a week or even a MONTH for something to air from the US, it boggles the mind.