I don't deny that this is double dipping, but our intuitions about double dipping might not be universal.
For example, in America, it is taken for granted that you pay for both incoming and outgoing calls. Koreans, on the other hand, would find it preposterous. Why should the callee pay, when the caller is already paying for those minutes? It's the same situation, but reversed.
Do you imagine people approve of having to pay for incoming spam calls? The idea is near-universally disliked, excepting telephone companies and politicians.
South Korean ISPs may have market failures, but it seems like in this case they wouldn't be able to do this without the regulation. This is all guessing based on context, but it seems like they don't want to play the risky game of blocking traffic, so companies could just ignore any bill they get sent. By having this regulation they can send a bill and have the courts enforce it if the company wants to do business in South Korea.
No not really. It cost something to host the pipe to customer, customer should bear this cost. And then it also cost something to allow access and utilization of ISP network. Reasonably this should be paid by whoever sends the data. If the sender owns a network they could negotiate peering contract where data send to each other is offset and then after some period either one pays to either.
Sender, and receiver pays them to pay that. So in this scenario the users of Twitch should pay for the sender to be able to send data. I see no reason why Twitch would not be charging for using their service in this scenario. And then viewer can pay for it.
