Digital content is much more ephemeral than people realize. Say you were on a forum with some friends a decade ago and you all made silly memes with inside jokes only you and your buddies would get. That content gets maybe a couple dozen eyeballs. If none of you save it it's going to get lost. The forum will shut down, people will go back and nuke their post history because reasons. its nice when you're having a bad day to go back into your screenshots folder and see all the silly stuff you did with your buds. It's the digital equivalent of paging through an old photo album.

The next reason is the instability of user generated content. Youtube purges more and more content by the day to please their advertisers. Big creators like PewDiePie will always be relatively "safe" in terms of disappearing. They have so many eyeballs on them somebody else is bound to be saving everything they do down to the twitter post. It's the smaller ones you have to worry about. Even if other people archive what they posted the chances you'll run into them to grab that archive is slim and it only gets worse the smaller the audience is. It's on you to save that because you don't know what the future holds. Youtube could terminate them for any number of reasons. If they self host it's "a bit" safer but it won't protect them from accidentally wiping their content without a backup... By far the most common occurrence is that they quit and an issue like this comes up: they get copystrikes and can't be bothered to fight them, they don't feel like paying the server bill, or they were a bit too edgy in the content they made and need to scrub the internet to keep themselves employable. I'm sure somebody somewhere has a copy of some content I consider "lost" but good luck finding that person. It's much better to be proactive about it.

It makes for a fun little hobby. I love computers and weird internet things so it's something that keeps me occupied and content when I have nothing better to do... And Plex.