I think you have to see someone who has used it for a while (or use it for a while yourself) to understand.
To me nano is just a basic text editor (open, edit, save). Vim is a way to 'jack in' and be able to manipulate text with my mind. I don't 'think' anout how to accomplish something, I just think about what I want done and my hands just do it.
This comes from the modal nature of the editor and text objects, mostly, but there are so many other little things (like macros, ex commands, filters) that you pick up over time that all add up to a great text manipulation toolkit.
Are you being serious? Vim offers so much more advanced features. But if you don't have a use for those advanced features of Vim Nano is probably more than enough for your use case. I just find Vim more enjoyable to use even for simple tasks since the commands are already in my brain and I really prefer the modality.
After using both I settled on Nano years ago and still don't see how my workflow would improve with Vim.