Trial versions don't work for all games. Sometimes the value of a game is in the controls and the wow you feel when the experience is still new. It's easy to give out the first chapter of a book and ask you to pay to read the rest of the story. It's different to give a tasting of the finest cognac and then ask you to pay for a whole bottle. The first taste is the greatest impression, and sometimes it's all you want. This doesn't mean the first taste has no value, it's certainly a great experience. That being said, I don't have a definitive answer regarding trial versions