Two reasons:
1. Valve provide a proven infrastructure to support the availability of a developer's product, along with MP features and various "engagement" APIs.
2. More important, Valve provide a developer with access to, perhaps, 200M people that are pre-qualified as being videogames players. In sales/marketing terms, these are "pink" customers that are known to buy what you are selling, compared to "blue" customers that are unknown random people. Typical conversion of a blue customer ( from, say, broadcast advertising ) is < 5%; it is much higher for pink customers.
Valve simply copied the 30% take that Sony and Microsoft charge developers for access to customers of their consoles.
There have been various challenges to the amount Valve take. For example, EA stopped releasing their games on Steam years ago because they didn't want to pay 30%, and they have Origin, but likely lost many sales because of that choice.
Since late last year, EA returned with their games to Steam. This is most likely a result of Epic Games setting up their games store with a much lower percentage take, which forced Valve into reducing their charge for high-sales games.
Edit: Buying on GOG also involves a fee, it is not free.
Last edited by etonbears; 25/07/20 08:05 PM.
