Having seen what these negotiations look like from a technical perspective, I can see why they want to do this. A lot of the old contracts are causing issues when they want to go to streaming, because they aren't clear as to what platforms the license is for in the first place. This is why sometimes some music is replaced or a scene with a particular guest actor is cut from the streaming version of an old show.

These changes are effectively future-proofing. By making these contracts apply to all platforms now and in the future, including platforms that might be impossible to maintain individual accounting for each show, it makes it a lot easier for them to exploit the content in new ways in the future without having to track down all the old actors, their estates, and their agents to negotiate new deals.

It probably will also suck for the actors as it will limit their potential upside while providing them with more money up front, so you'll have fewer crazy rich actors but more middle class actors.