To be able to serve the static content through providers that cache files to minimize bandwidth. All request needs to be unique to the file and change when the file changes.
An example of an easy way to do this is to add a garbage query parameter with garbage data, like the md5 checksum of the file. Or a timestamp of when the files where generated stored in the json file. Making the url unique for every file when it changes.
/zoom_0/tile_0_0.jpg?static=<checksum>
I have no knowledge with leaflet so I don't know if this is possible.