This isn't true either.
Randomly picking a handful of not high profile WiiWare games:
Target Toss Pro: Bags - 1 review
Bit Boy!! - 4 reviews
Yummy Yummy Cooking Jam - 2 reviews
Tiki Towers - 2 reviews
Spaceball: Revolution - 8 reviews
WiiWare games do not have demos.
Randomly picking a handful of not high profile XBLA games:
Geon - 13 reviews
Roogoo - 20+ reviews
Axel and Pixel - 20+ reviews
Boogie Bunnies - 20+ reviews
Double D Dodgeball - 20+ reviews
All XBLA games have demos.
Can we agree that it's much harder to get to know (non high profile) WiiWare games, much harder to get to know what other people think about (non high profile) WiiWare games, and that this contributes to people having a worse attitude towards them?
Edit: I also think that saying that people ought to do research is a little silly. There are more games across all consoles than there is time to play them. Most people who are big enough into gaming to take a chance on niche titles already have backlogs. If one service is less accessible than others, that burden is on that service to resolve that. I'll always have games to play, the question is whether I'll have WiiWare games to play.