These programs are often made by commercial entities (like BBC Worldwide, which is separate from the normal state funded BBC) who license their material to foreign streaming services like Netflix.

If every impactful documentary would be given away for free, there's no incentive for anyone to pay the company behind it to make more. Journalism is expensive and I don't think enough people would donate to a large corporation through Patreon.

I would love documentaries like these to be available without restriction, but when it comes to copyright and business model, it really does come close to Moanna or Eastenders.