It's usually because of what I wrote in my previous post. If you have 10 MMO's/FPS's games out around roughly the same time, some of those games are going to be worse than their competition. No amount of demos/free trials or piracy protection is going to help those games better their sales ratings. These statistics shown in the video you linked are statistics from a market with fierce developer competition during times when piracy is at it's strongest.
Everyone is essentially making the same game at the same time, aimed towards the same audience just because statistics show that gametype is popular right now. So of course putting out a demo showing the world that their FPS game is worse than their competitors FPS game would be developer suicide. This is where the famous MW vs BF feud comes from. Both publishers put out the same game at the same time to attempt to steal costumers from each other. It's a destructive and stupid sales tactic that is doing harm to the gaming industry and is in my opinion the very reason we can't have demos.
It's because of greedy and afraid men in suits with statistics it's so hard for games to succeed in today's market. It has nothing to do with the consumer being picky.
---------- Post added 2013-03-11 at 11:38 PM ----------
Just to add and make it clearer: You don't place your hotdog stand next to another hotdog stand. You don't open a jewelry store across the street of another jewelry store. You don't sell your FPS game at the same time as your competitor sells their FPS game.
This is exactly what's going on today and what's been going on for the past 5 years when the market suddenly became fierce.