Why on earth?

I think the idea of this is to give you an idea of how they do sound. What really to me is a waste of time is to have a reviewer talk endlessly about his impressions of what he heard without a demonstration. You should be able to get an idea of maybe how they do sound because you are familiar with how your speakers present the sound that you have been listening to on the youtube video. Otherwise they are just moving air and wasting time to me.

What you get is a crude combination of the characteristics of your playback system and room acoustics layered on top of a crude combination of the poster's system and room acoustics, plus the very crude characteristics of the microphones employed and recording techniques, etc.  It is ridiculous to then try to isolate the difference one piece of gear makes in this mess.  A friend of mine toured a recording studio and was shown a room full of microphones.  There are some artists who will request a very specific microphone--not a particular brand or model, but a particular microphone because the difference matters to the artist.  Do you think any of these posters have that kind of selection and special microphones to capture the essence of the gear being auditioned?

The testing folks are also a bit unrealistic.  They often post frequency response, waterfall plots, etc. of speakers and comment as though those tests give definitive results.  Wholly apart from whether the tests really measure what we perceive and like, the tests themselves don't accurately measure what they purport to measure.  Manufacturers looking for good measurements send their gear to a testing lab in Washington state that is built inside a nuclear reactor facility that was never commissioned.  The main testing room is behind many feet of concrete and the room is gigantic (something like 450 feet long and wide).  The testing facility certifies that it can accurately measure speaker frequency response down to 25 hz.  Now tell me how some backyard or garage setup can give accurate measurements.

Generations of yoots loved the sound quality of mp3, those golden ears are still out there, they hear differences we cannot possibly hear. They can probably hear the magic difference of various fuses in equipment online.

A very good question your phone,or tablets monotone speakers suck!

the only thing I can see is showing you features or the design and components 

which have some merit, as far as music 🎶 it is a moot point ,pointless literally !!