I wouldn't be surprised if there's a TOS clause about videos on YT not being your property and that you can't export them off the platform unless you own the rights to the specific video. People that watch videos on YT are using someone else's platform; don't like it, don't use the platform, and tell the content creator to upload somewhere else. Nobody is entitled to bypass intentional blocks by YT and use 3rd-party tools to download other people's videos.
Personally I only used youtube-dl to pirate songs from HQ videos :p I can't imaging there being a large percentage of "legitmate" and fair usage.