When my full-time job was as a journalist, I used youtube-dl all the time as a way to have archives of content that was either in danger of being taken down (related to a mass-shooting or other global event) or that the creator would take down after it received attention. In fact, I used to have instructions for how to install it in the various wikis/docs for other team members (this was easier once the Python GUI frontend became available, but I still created step-by-step instructions for specific settings).
I produce/host a few weekly news shows focused on developer-centric news and updates and have a keyboard macro setup to run youtube-dl against a text file with URLs not to download the videos, but the thumbnails for videos, so I can use them in the on-screen graphics when talking about a specific story. Before I scripted that solution, the process of having to manually extract the thumbnail for any video I was highlighting was a major PITA.
Also, being frank, youtube-dl is significantly better than the official YouTube API for downloading past content from channels I own/manage. It’s faster and a lot more scriptable. I have automated scripts set to watch specific playlists or channels and auto-download stuff for archival purposes — and again, this is content that I either own or that exists on a channel where I’m one of the admins.
It’s unfortunate that the test suite had links to commercial music — we’ve seen in past RIAA litigation that that is enough to go against the argument that this isn’t encouraging download of copyrighted content.
But as a tool, for not just YouTube but so many other services, it’s invaluable even in non-data hoarding/grey area or straight up infringement scenarios.
To be clear, I’ve often used youtube-dl to infringe (as have the vast majority of its users), but that’s my choice/fault. The tool itself has plenty of non-infringing uses. I just wish they’d either linked the test file to another area or used other examples.