Fine, so tax it. This doesn’t amount to a pro-argument that someone else should be able to divert my income stream and my creative work for their own private gain.
The big extensions came in the mid-70s and late 90s, well within living memory. According to your own link they nearly doubled the average duration and pushed it over 100 years.
> What’s the compelling argument for them to exist as is?
You’re asking why does copyright exist?