Earlier quoted context omitted.
The problem that Reddit's native vid/img upload solved was how every Reddit thread older than a year was a 404 link to imgur, a Youtube video since made private, etc. It's essential to avoid link rot. Not long ago, old Reddit content was almost always dead. As usual, it's just trade-offs.
Shouldn’t the creators of the original content have a say though? If someone made their youtube video private that probably means they don’t want people watching it anymore.
Even super small businesses that rely on training videos as paid income don't host things on YouTube because they want more control over the content.