Interesting. I can see that point and it has been brought up by a few people. I have to ask though, why are the (lots) of videos not enough in your mind? Are they really not and does a free demo help or people just want it because "it's free"? Why is it so common to put those out and many people now expect them as standard?
Also - I think most people love to get a fill of the game themselves... That's why even big games release a demo or some kind of playable game (like Detroit, for example) just so people can see if they like the mechanics (even the basic ones) or the vibe..
I think doing a demo is a bit like doing an expo - just on a wider scale