... until you want to offer directory structure a with multiple files

In the "transition" from FTP to HTTP, the level of abstraction in popular use has shifted out of the protocol and into resources (mime-types) [1], rel types [2], server logic [3][4], and client logic [5].

In the past, I've said that this extensible nature of HTTP+HTML is what made them so successful [6], but once specialized protocols began to falter, tunneling other semantics over HTTP became not just a niceity, but also a necessity (for a diverse set of reasons, like being blocked at a middlebox, being accessible from an the browser where most people spend their time, etc).

[1] http://www.iana.org/assignments/media-types/ [2] https://www.iana.org/assignments/link-relations/ [3] https://wiki.apache.org/httpd/DirectoryListings [4] http://nginx.org/en/docs/http/ngx_http_autoindex_module.html [5] http://stackoverflow.com/a/28380690 [6] https://news.ycombinator.com/item?id=12440783

So, configure your HTTP daemon to serve directory indexes, and point it at the root of whatever tree you want to serve.

Apache works better for this than FTP. I use it all the time: just configure it to serve indexes. Apache lets you configure the index to include CSS, fancy icons, custom sorting, and other stuff. All over HTTPS.

What's not to like?

Because then I need to use a browser plugin to download all the files in a directory.

True. Or, you know, wget.