When I make a request like that, people usually open Internet Explorer.

Windows Explorer includes the Windows desktop, so it is literally impossible for people to use Windows without using Windows Explorer. Yet I have still found people who are limited to double clicking on icons to start a program or open a folder. Most of the people who I've worked with will be able delete, copy, and rename files as well as create folders when asked. Yet a good number of those people don't use Windows Explorer to organize their files on a regular basis.

So yeah, it's quite possible that most Kobo users won't know what a file manager is. That's becoming ever more true as software starts taking over the responsibility of managing files for the user.