It's a good question and one not answered by the README. The very first thing I add to any README now is a heading "Why?" (usually along with "What?" (is it)) because I often land on a piece of software's home page and after reading I still don't know how it would benefit me or why it has been created. The easiest way would be a before and after kind of thing but just a line or two can be a help.

The 5 W's[1] aren't just for journalists.

[1] https://en.wikipedia.org/wiki/Five_Ws