If you write a book you should have rights to how that book is distributed. That’s the idea behind copyright.
Copyright is all about preventing anyone else from profiting off of your work by simply copying your work. Thanks to Mickey Mouse that duration is now life+70 years which is absurd.
Distilling the concept down and removing the nuance: As of today if you produce a written work you have monopoly control over that work for life+70 years unless you sign contracts stating otherwise.
Today, copyright as a construct creates monopolies that survive the creator.
In the case of Drug copyright, the duration is 20 years from the invention, which generally ends up being about 10 years after clinical trials to make money before anyone can make a copy. I struggle to see why the rules do not evenly apply, but the rationale behind drugs seems to be that humans benefit from them being available for as cheap as possible. If we had 20 year durations on TV and Movie copyrights it would be better for the masses and would give creators decades to earn profits on their work.
Drug makers try everything possible to extend copyrights on their drugs by doing things like creating medical devices with superior delivery methods in the case of injectable drugs. Since the new delivery method is more effective the old one is generally not used and so generics have to then wait for the delivery method to be out of copyright... This is just one example though. There's no promises a generic drug ever comes to market if the drug is not widely used. The same shenanigans would be used by the entertainment industry to re-package their content with remastered versions or re-scanned original films like they have done with DVD, Blu-Ray and Streaming versions. Extended editions would also be an option... but the original copy would be free for all to enjoy after 20 years.
Why anyone is able to profit off of the original edition of Peter Jackson's Lord of the Rings for another hundred years is beyond me, it should just be free and available to everyone imo. The money has been made.
That's my opinion anyway. Monopolies and income in perpetuity are horrible concepts generally only abused by the few at the detriment of the many. In the real world many just pirate content anyway. If it were up to rights' holders NO copies even for personal use would be allowed. They would just have us pay per view even for copies we purchased.