Just curious because I don’t see people talk about it a lot.
Bandwidth is cheaper from the tower since the signal is the “same” for each client and it can then be distributed over a wide area. You send the “DRM” (Just a fancy encryption key) over the network since it’s relatively small and likely unique to each device (probably fingerprinting the device ids to the content invisibily in case of piracy).
Multicast is a thing, though it doesn’t seem to be widespread. That would make a lot more sense than this weird DRM broadcast system.