The most likely answer is: Tor Browser keeps these pages because there is no reason to remove them.
Firefox is a big, complex project with lots of components that depend on each other. And it keeps changing, both to make it perform better and to keep up with changing Internet standards. It is not really possible to just pick the parts you want; you have to ...
Know and understand the security-related implications of making this change
In the Tor Browser address bar, type in about:config and press enter
Search for privacy.resistFingerprinting.letterboxing
Set the option to False
Restart the browser for changes to take effect
Tor Browser 9.0 is configured to use letterboxing by default. The