It would kind of make sense for them to give owners the game on steam. If buying through their store gave you the license through their launcher plus a steam key, you might get more people to buy it from you without giving Steam their cut.

I know Steam doesn't give you unlimited keys, you have to sell on Steam in volume at some point, and you have a huge amount of licenses sold on your own platform already, but you could make people get in line if needed. You might even be able to work something out with Valve, with the belief that moving a sizable portion of the user base to playing through Steam brings them more value than 30% of the small handful of duplicate sales or sales lost to their storefront.