Lets say your html file points to two javascript files, app.js and lib.js. You make some changes to both files, and deploy. With browser and CDN caching, user

Lets say your html file points to two javascript files, app.js and lib.js. You make some changes to both files, and deploy. With browser and CDN caching, users could get the old app.js with the new lib.js, or vice versa, until the caches have expired. In other words, there's no guarantee that both caches will expire at the same time. This can easily cause mysterious and transitory issues which disappear before you can debug them, but reoccur after future deploys. This fixes that by ensuring that your html files explicitly point to a consistent set of css and js files.