There's a sort of joke in academia, about the "least publishable unit" for a paper: Since "how many papers produced" is much easier to measure than "impact on a field", one way to try to game the system is to figure out the smallest amount of research that can be called "one paper", and publish just that, to maximize the papers / research effort ratio.
What we're seeing now is the same thing for streaming services. Sure, you'd pay £20 for a subscription to watch 75% of all available content. But it turns out most people would pay £40 for two subscriptions, each of which would show you 35% [EDIT and even people who won't, will still pay one £20 subscription for 35% of the content]; and quite a few people would pay £100 for five subscriptions, each of which will show you 12%. The beancounters are busy experimenting to find the "least bundle-able unit", to maximize extraction.
EDIT: And as someone else has pointed out, this is not something that any Netflix -- or any potential replacement -- can unilaterally do something about. In fact it's a "tragedy of the commons" situation: If MGM and Universal Studios and Paramount and WB all license their content to Netflix (under the £20 umbrella), and Disney doesn't, then Disney gets to keep a massive amount of money for themselves, while the other rights-owners have to divide up the rest. It only takes one or two "defectors" to basically force everyone to do the same thing.
Or you can pay £0 per month for 99% of the content.
I'm a bit like the parent comment. I've always wanted to be able to pay a monthly fee (even a high one, say £50 a month) to have access to a good quality selection of movies and TV shows. The thing is, it's always bugged me that you can get a much better experience by pirating than by paying for legitimate access. That seems the opposite to how things should work.
This pre-dates streaming. DVDs came with FBI warnings and other screens that couldn't be fast-forwarded or skipped. You couldn't buy a DVD in the US and play it in a DVD player in Europe because the "region" didn't match. You couldn't easily transfer it to watch on a device without a DVD player because of the DRM.
All of this means that, even ignoring the fact that it's free, it's just far more straightforward to torrent a movie and watch it wherever you want using whatever app you want.
What we're seeing now is the same thing for streaming services. Sure, you'd pay £20 for a subscription to watch 75% of all available content. But it turns out most people would pay £40 for two subscriptions, each of which would show you 35% [EDIT and even people who won't, will still pay one £20 subscription for 35% of the content]; and quite a few people would pay £100 for five subscriptions, each of which will show you 12%. The beancounters are busy experimenting to find the "least bundle-able unit", to maximize extraction.
EDIT: And as someone else has pointed out, this is not something that any Netflix -- or any potential replacement -- can unilaterally do something about. In fact it's a "tragedy of the commons" situation: If MGM and Universal Studios and Paramount and WB all license their content to Netflix (under the £20 umbrella), and Disney doesn't, then Disney gets to keep a massive amount of money for themselves, while the other rights-owners have to divide up the rest. It only takes one or two "defectors" to basically force everyone to do the same thing.