I have seen so many reviews on youtube that include the listening to speakers/subs/headphones and each time I have been thinking that it must be a joke, but it is not. They even do comparisons in those videos! Like you say, you can't even get the slightest idea how they sound or compare from listening to those videos as it won't sound even relatively close to what it is supposed to sound. However, it is sad that quite many people seem to believe they know how speaker sounds after they have watched those youtube videos and they may base their decision on those videos.