Here is a review of what this "index of" method is, how it works, and why it remains a popular (though controversial) way to find content. What is "Index of mp4"?
People with slow connections who prefer to download a file overnight rather than stream it with buffering.
When you download from a random server, your IP address is logged by that server's owner. You have no way of knowing who is watching the traffic. The Better Alternatives
However, this accessibility often exists in a legal gray area. While some directories are maintained by educational institutions or hobbyists for legitimate sharing, many are unintentional leaks or hubs for copyrighted material. This creates a cat-and-mouse game where servers are frequently taken down as quickly as they are indexed. The Preservationist Perspective