I always thought it was a rule that it had to be on terrestrial TV. Let's be honest, who's going to give a shit about the Olympics in the future if it becomes a fully PPV event? Who's going to have heard of any of the Olympians if the only people that watched it were the few hundred thousand who were willing to pay 30 quid to stream it (or more when it's exclusive).
Incidentally, what a load of shit. It's an event in which the athletes aren't paid to compete, everything is largely publicly funded from the infrastructure to the training of the athletes, but then the thing that everyone has paid for is put behind a paywall by some big American corporation.
Reminds me of academia. The public funds it, but if the public wants to read the research, they have to pay a big publisher who contributes fuck all to the process.