> serving static files has never been a problem

I address this in the post; there's no problem with it, but it requires that you (or your end users) come up with a solution for deploying static assets to production, figuring out the relative paths between the working directory and the asset directory, and ensuring that the right version of the binary loads the right version of the assets. An example of the type of difficulty here is that you couldn't remember how to do it off the top of your head.

If you compile them into the binary, you (or your users) don't have these problems.