To your point about computing power, I think it's only now that it's reasonable to not filter the duplicates. If I want to emulate the dedup behavior it's trivial nowadays to blindly read 1M lines of history and dedup on the fly each time. Using downstream tools doing duplicate filtering/transforming work is similarly very very fast. Disk is cheap enough that I really do want to keep every command I ever write in my history. More expensive compute and disk would make me more likely to turn that feature on, not less.
And I want my history untouched, because sometimes I forget how I solved something, go back a few months in my shell history and see the sequence of commands that I've used. I think that's a nice thing to have. And if I ever need history without duplicates, it should be easy to deduplicate it with a simple script.