[opk]

The shell's defaults are conservative because when you change the defaults you change the setup of many existing users. So unconfigured, the shells feel much the same as they did thirty years ago.

There can be other reasons for wanting a smallish history besides fast startup like wanting low history numbers if you learnt all the ancient `!` history escapes that were the main way of using history with csh going back forty-plus years ago. This is also one of the reasons why extension theme frameworks like oh-my-zsh have become popular - much of what they do is enable bells and whistles that are features of the core shell.