I dont think developers help themselves, if they dont release demos prior to the game release then loads of people arent going to fork out £30 on a game they havent played that may not be any good. Thanks to current steam/origin rules you cant trade them back in. So whats the option? - pirate it, play it weeks before general release and see if its worth the asking price. Console players have it easy, if theyre not sure about a new release, rent it from blockbusters or similar for ~£5 and decide.
If the individual that pirated it, actually then pays for a genuine version is impossible to say and I guess we'll never know but unfortunately thats the way it is. Until developers learn this and release demos then it serves them right.
Imagine buying a new car, would you still buy it if the salesman said no you cant have a test drive?