system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does youtube work now? Why does it no longer fully buffer when paused. Why does it have to reload when I rewind to something I've already watched?
gpt
To the first point: for whatever reason, and there are loads of analytics to back this up, most people don't want YouTube videos all the way through, especially when they're over about 10 minutes in length. So Google realized they could save bandwidth by greatly reducing the amount of buffering they did for videos.

To the second: most likely a combination of browsers throwing played video out of cache and YouTube trying to do the same thing for them, as an optimization.