Everyone benefits from the idea that killing off the copyright holder is not profitable. If copyrights expired on creator death, there would be unwholesome motivations.
Honestly, I find it difficult to understand why a fixed 40 year term isn’t long enough to benefit from copyright. Trademark is already indefinite, JK Rowling is hardly going to be meaningfully harmed if someone publishes a work based on the first Harry Potter book in 2037. Less wealthy authors generally need to keep working anyway. Publish a hit at 22 and perhaps it’s time to start saving for retirement just like everyone else.
The current law is still extends the copyright of a work until a time after the author's death. So if one wished to hasten the expiration of those rights, the motivation still exists; although perhaps diminished by a 70 year wait.
Which are life imprisonment for murder. Not some magical "my children must be fed millions without ever working until 70 years after my death".
Seems a lot of risk and effort for a small chance of profit.