Renegotiating the contracts would require lengthy and expensive processes of discovering the proper parties to actually negotiate with in the first place.
Although the contracts that were already executed can be relied upon, it truly is a can of worms to open, because it's not "Renegotiate with Studio X", it's "Renegotiate with the parent company of the defunct parent company of the company who merged with Y and created a new subsidiary Z" and so on and so forth, and then you have to relicense music, and, if need be, translations.
Then repeat that for each different region you need to relicense in because the licenses can be different for different regions.
The cost of negotiation would be greater than the losses to piracy tbh.
It was invented to protect publishers (printing press operators). That continues to be who benefits from copyright. It's why Disney is behind all the massive expansion of copyright terms in the last hundred years.