Disclaimer: I enjoy streaming and dislike being forced to watch advertisements. :)
Indeed,
the "big companies" each have enormous catalogs of content. However MUCH of it played on primary, secondary and even 'retro markets' already at some point in the past.
Hence the 'marketability' of much of it is limited at best making its 'value' and 'cost' to those that wish to offer it equally limited at best.
Here Netflix had a winning formula where they bought the rights to distribute content that few others had any interest in and packaged it all in a inexpensive package that almost countless viewers found compelling enough to buy into.
The sheer volume of content that WAS available on Netflix for commercial free viewing was to attractive for many to pass up.
Fast forward to today where the content owners have pulled MOST of their content back for their OWN streaming platforms and now consumers/viewers have a multitude of streaming options, ALL OF WHICH have very limited content.
Many of (if not ALL) the streaming providers include advertisements.
Personally, I wish the majority of them would simply GIVE UP and return to licensing their content to Netflix.