http://www.vg247.com/2013/02/11/releasing-a-game-demo-can-cut-your-sales-in-half-warns-schell/ So it completely makes more sense to sell something to blind consumers and take advantage of their ignorance before their buyers remorse can set in. GOD FORBID THEY FIND OUT THE GAME IS ACTUALLY BAD AND ARE PUT OFF FROM BUYING IT, OR BETTER YET THEY FIND OUT A GAME IS ACTUALLY FUN AND GO PRE-ORDER IMMEDIATELY!
It's how capitalism works. If there is a chance to increase your sales, you take it, even if it means the customer ends up less than satisfied. If you can do that by keeping your customers ignorant about your product, that's what you do.
i can see why that is. i can think of plenty of times a demo made me not want to buy a game. for example, i was pretty turned off by the Playstation All Starts demo and never bought it. there have been times when a demo made me buy a game i wouldn't have thought i would like as well, though i can't think of any off the top of my head.