Quite a few apps on Linux depend on Python as their go-to extensions/plugins language. Here is a small sample

    nearly all the system config GUIs relased by Redhat
    inkscape
    quodlibet
    csound
    ntop
    samba
    ranger
    libreoffice (but this supports a few other languages)

Try to run any modern Linux distro and tell me how far you get without installing Python.