They care because they are going to be made legally liable.
It would be a big hurdle to make them legally liable. The content owners would have to prove that it is possible for them to stop it and at minimal effort or cost, and still I don’t think there are any damages to recoup.
I agree with the poster above, it has to do with money, but imho they have to be angling in some way to get cut in on the transaction. I figure they think along the lines of “Why should Apple and Netflix etc get 30% of every movie and we who transmit it and maintain and expand the infrastructure to make that possible on a large scale get zilch for the effort?”?