The implicit promise -- actually, occasionally made EXPLICITLY in marketing -- of high-speed broadband was that everything would be available, but the reverse has proven true. A person living in an urban area had a larger selection of movies available for rent in 1999 than they do today because the first sale doctrine protected the video rental business, but streaming is governed by different agreements -- which leads to ridiculous "availability windows."
We mostly use Apple's movie rental system, because the quality is better than Netflix, but you still get the availability shifts. Sometimes something won't be available for rental anymore, but remains in the list as a purchasable (ha) item. This is just straight-up rent-seeking bullshit, and it didn't (and couldn't) happen when movies were tied to a physical object.
If you want a deep library of rentals, DVD/BR by mail is still better. If you want better quality, DVD/BR by mail is the best option. And obviously if you live somewhere with shitty connectivity (basically the entire rural US), then by-mail might be your ONLY real option.