There is not just that. Another big reason is that youtube, despite all theirs tries, have never been able to separate their music part for which they want to sell subscription, from their video part.
And some of the things they need to do to push subscription on their music premium thingy are contrary to the things they need to keep quality on the video side of things.
For exemple, easily playing the video from an artist channel (or the many channels publishing music in a genre or publishers etc ... like Suicidesheep, NCS, Proximity, ...) is not something they want.
So what did they do ? They removed the "play all" from the "uploads" page of a channel. This button played what was essentially a playlist of all the uploads of the channel, also allowing you all the playlist tool (repeat, shuffle, ...). Because you're supposed to do that through a youtube music (or red, or whatever the name is now) subscription, they gutted it, and now there is no way to easily watch all the videos of a channel unless the channel owner curates it himself into a playlist.
(usually, music publisher channels have a playlist by genre/subgenre, or artists one by album etc..., and had the automatic "uploads" playlist for all of it, so they did not have a specific playlist for everything)
As a side effect, you can't do that on video channel either anymore, oupsie !
(the reason I believe it was done on purpose for music is because there is no gain to change that for video channel, quite the contrary: if you use that feature on a video channel not only are they retaining you, but they should also be able to target you much more accurately with their ads, eg if I'm watching all of "mandalore gaming" videos then video games ads are clearly for me)