Do I really need it?

I have been aware of calibre for a long time but I never installed it, because I can't see what problem it would solve for me. I only read free books from Gutenberg or Standard and only in epub format, so I don't need conversion. And to move it to the reader device I can just connect it with a USB cable and it automounts as USB storage, then I just use cp or mv from a terminal. Which is what I also do to "manage" files in general, and not any GUI file manager and not even anything like MC.

Am I missing something?