I mean, there are options. It could mute/unmute, close the stream, copy one of various track information such as track name or playback position, send the video to different screen etc. But I can't think of anything that makes much sense, although mute/unmute is at least somewhat sensible.

But, yeah, it's one of those interactions that has just always worked like that, long before browsers could play video even. It's similar to how Ctrl+C copies stuff, Ctrl+Z undoes previous operation, right-click opens a context menu etc.; they don't have to do those things, but users have learned to expect it, so it would be pretty dumb to change that with no reason.