It's not really in contention that Steam is the biggest platform on PC for video games. What's slightly in contention is just precisely how big Steam is - or rather, how many countries it's in.
According to the about page on the Valve site, Steam is "is available in 237 countries and 21 different languages". It's actually 26 if you go to the language preferences part in your Steam account, although that part of Valve's website probably doesn't get a great deal of attention.
But 237 countries? That seems a little ambitious. There's only 192 member states in the United Nations, which doesn't include Taiwan, the Vatican City, or a range of other countries that are recognised by some states but not others. If you want to get down to the finest figure, 206 seems about right.
It's certainly not 237, something Federal Court judge Justice James Edelman pointed out this week when ruling against a Valve request for confidentiality orders:
Initially, Valve submitted that it was confidential information that Valve was a very profitable enterprise. I explained that this bold submission was made despite Valve itself boasting on its website that Steam is the world’s largest online gaming platform and that it "connects its 35 million active users to each other" and that it is "available in 237 countries" (a claim which displays a curious understanding of geography).
At the time of writing, none of the Carmen Sandiego games are currently available on Steam.
Question is: what are all the extra 31 countries that Steam thinks are legit? Without a VPN active, Steam will only allow Australians to change their country of origin to the United States (a proviso for military serving abroad). But if you're a user in one of those fabled countries, let us know!