I find it peculiar to ask this question but then also deduplicate your history file because then you lose complete history and context. Sometimes I've had to issue series of commands to fix a particular problem (changing a kerberos password, fixing the expiry date of a gpg key, etc.) that I can backtrack through the history file to find what I did and how I resolved it, later having to do the same, and according to their settings the first instance would be removed.

Personally, I can't remember the solution to everything I do so having that deduplicated log gives me the full history of what I did and how I resolved it, amongst other uses. Sure, removing duplicate 'ls' entries is fine for example, but for every command? Not so sure.