I understand and support your reasoning, and agree that games really should come with a trial that you can sample before you commit to purchase. In my opinion it could only help sales, as it would give gamers security pre-purchase that they are going to buy a worthwhile product, but when you have no demo to go off of, it is kind of like buying a pair of shoes without seeing if they fit first.
I don't support the torrenting of games myself, and I bought my copy off of GOG yesterday, but still I support your reasoning. I'm just glad we have a website such as Youtube, to give us a great indicator of what things are actually like.