Yes that is the big issue with this video platforms. Video streaming is a demanding task. And I can’t even imagine how much storage would we need to have something remotely similar to YouTube. Google was able to run YouTube because it had free money coming in , now the funds are drying up so more ads coming their way.
So since Real Debris just like YouTube its a legal service , if you upload a movie to YouTube and a company send them a notice to take down that movie , YouTube will take it takedown and company happy :) the same is with Real Debrid.
This is what I found from a Reddit comment: Debrid services literally are just like if you downloaded from the share website directly, as if you had signed up for an account with them. And/or the debrid service downloads the torrent on their server, and you stream from it.
This is already protecting you from any potential legal issue.
Some people may get warnings/potential legal trouble for torrenting directly, but this is only because when using torrent you also become a hoster of the content yourself. This doesn’t happen with these.