It means that selling their game is how game developers earn a living. The mobile version is free with ads (which pay for the game). Advertising isn't a standard feature of PC games so they sell the game on PC instead.
ARE YOU A FUCKING COMMUNIST?! ARE YOU BEING SMART WITH US?! YOU DON’T EVEN KNOW THAT THEY NEED IT BECAUSE YOU ARE SUPPORTING THEIR HARD WORK! AND YOU ARE HATING IT?! WELL GUESS WHAT KID? I HATE YOU!
