I don’t think people nowadays can comprehend how basic the OG Napster was. You searched for a file and every single person with a matching file would come up as a separate result. When you downloaded you downloaded only from that one person and if they cancelled it or whatever before it finished then it was gone and you had to start again. You couldn’t resume, not even from the same person with the exact same file.

Memory fails me, but I want to say that the idea of a re-download finding the end of file and resuming went back even further in history (Zmodem I think was my first exposure to it). The creation of such a miracle was game changing for the very reason OP mentions, along with other interruptions.