Why is Warner Bros. Discovery putting old movies on YouTube?

Anything from before the 1980s should just be on YouTube, its easy cash for them on films that are sitting idle otherwise. Anything they aren't licensing to anyone anywhere should just be on YouTube. Or any sort of streaming platform that has sane ads, and anyone can see. It is really sad to me there's no genuine YouTube competitor.

"you should just do X" generally means you don't have the full picture. You're completely disregarding all the union stuff that needs to be considered. You're forgetting all the little guys that make movies happen. Yeah the directors and actors probably don't care, but the other 100s of other people involved in making films probably do.

Edit: You're right. Just disregard any laws and contracts in place. HN knows best. It must be that easy.

Are the little guys receiving royalties from these movies decades later? I recall instances where actors paid some of the little guys out of their own pocket to keep movies going, Deadpool is an example of this.

Yes, I'm pretty sure they do.