Perhaps they wanted it to work even when offline? It can be a struggle to get basic browser caching to work nicely in online/offline scenarios. As arethuza po

Perhaps they wanted it to work even when offline? It can be a struggle to get basic browser caching to work nicely in online/offline scenarios. As arethuza points out though, that is better addressed using appcache. I could imagine doing something like this if you wanted to support say es6 modules, and so each file needed to be processed after it was loaded to work in the current browser. In that case, I can imagine wanting to cache a processed one on the client side, although if you control your whole stack, it'd be better to do that work on the server.