Companies have a finite amount of money.
If the DVD and Blu-ray rental userbase is dropping, I could cut that division's budget in half and move it to another division that is generating much stronger traction (eg. Netflix Korea and their KDrama acquisitions making Netflix a market leader in Asia).
The TAM of the DVD/Blu-Ray rental market has fallen, so as a company, it's best for me to fire those customers - either by slowly degrading the service so they change to the mainstream service, or deprecating the entire service.
> 100k titles. No streamer has that.
But
1. Do does a large enough userbase actually want that?
2. Can that large enough userbase spend enough margins on that service to generate a healthy profit?
3. Are my operating costs for that division rising faster than the revenue from that division?
If all 3 of those answers aren't satisfactory, you end up shutting down an initiative.
Also, there's always FMovies or Pirating for those who really really want it.