All the good reasons for compressing music or audio in general certainly apply to YouTube. The average viewer will probably listen through laptop speakers in a noisy environment, and a large dynamic range is not helpful to them.
Also, does this mean they actually lower the volume of high RMS/LUFS videos?
If you use compression on the assumption that a chunk of your audience will be listening on shitty speakers you ensure that anyone not listening on shitty speakers also gets a shitty experience. Perhaps Google would like YouTube to be a non-shitty experience for people with nice speakers (or headphones or whatever).
The right answer depends on the content, context and audience. The choice is with the content creator, not with YouTube, and for many content creators optimizing for people with bad speakers is the right choice. Lowering the volume is not going to make "shitty" compression unshitty.
This hyperbole serves no one. Modern limiters are tremendously transparent, and only people who are listening for it will notice the increase in compression.
That said, there is a case to be made for listener fatigue. Personally, I'm not on youtube for extended periods where that would be a problem, but I can see how it might be. Further, as a musician and engineer, I have long had to live with the fact that none of the streaming services (not even iTunes the app) are transparent. After having spent days on a mix and master, it's quite a shame I don't get to decide how the exact final product is sonically presented.
Agree. Though, I'd add a qualifier - "...are tremendously transparent when used correctly..."
The one thing even audiophiles with the best speakers on the planet need to realize is that no speakers can approach the dynamic range of what modern digital audio have to offer us. Therefore, some tasteful compression (or limiting) will be needed, or the signal will launch the speaker cones out of their baskets.
Compressing music (in the loudness sense) at the source is never a good thing for the consumer; if it is required for a specific end user case then it should be done at that point rather than ruin music for every use case.
I don't buy for a second that it's necessary or helpful with the music that it is done to; which rarely has quiet passages. Compare the two masterings of Pharrell's "happy" I posted, the less compressed version sounds far better even on my 11" laptop's speakers, which should be pretty much 'as bad as it gets'.
Even the cheapest headphones make halving the dynamic range obvious on typical top of the charts pop tracks.