Good thing, python2.7 is deprecated and no longer receives security updates, and a lot of Linux distributions (Arch and Fedora for example) plans to remove it from the main repositories at the end of this year, so having it installed doesn't make sense.
Even the perl and ruby version installed is old, and nearly nobody uses perl or ruby at this day. Maybe perl is still used by some programs and scripts, for example TexLive relies on perl, or ruby is used for brew. But you better installing more updated version yourself so removing it is not a big deal.
There is no meaning to keep old script interpreters installed, if you want to use them you probably want to install a more modern version, if you don't need them it's better to not have them.
Homebrew (after installation) uses its own, bundled ruby runtime and will finish removing any dependency on system ruby long before Catalina is publicly available.
I know, but this wasn't the case when it started. Besides, I believe the parent's point was that nobody uses ruby or perl for anything anymore, regardless of whether it's preinstalled or not. Which is obviously silly when looking at homebrew's internals.
Even the perl and ruby version installed is old, and nearly nobody uses perl or ruby at this day. Maybe perl is still used by some programs and scripts, for example TexLive relies on perl, or ruby is used for brew. But you better installing more updated version yourself so removing it is not a big deal.
There is no meaning to keep old script interpreters installed, if you want to use them you probably want to install a more modern version, if you don't need them it's better to not have them.