It's not about media or taxes, it's about inflated fees for traffic period. It's regulatory capture (which Korea has a long history of) and subsequent collusion by Korean ISPs. Prohibitively expensive to run a streaming service like that even if you have local datacenters to reduce international transit fees (because you still have to connect to the local ISPs who will still charge you). https://carnegieendowment.org/2021/08/17/afterword-korea-s-challenge-to-standard-internet-interconnection-model-pub-85166

Edit: To be clear, this sort of situation is about the only one where to effectively have a streaming service, you'd need to use peer to peer and make it "come from inside the house", so to speak. Even their local streaming services are over the barrel and only the ISPs themselves could actually make an affordable streaming service.