I put this in the same category as non-premium cable networks airing movies or doing marathons of shows. Sure, they're on DVD/Blu-Ray/etc, and probably streaming somewhere. But if someone's looking for something to watch on the TV, and they see a movie they like, some people will watch through the edits and the commercials rather than get out their disc or switch to the streaming app. Presumably that's enough in some quarters to make purchasing the rights a value proposition.
Similarly, if someone's watching a Freeform original, and The Office comes on next, I bet Freeform is gambling that enough people will stay on their channel to make the rights fee worth it.
David