Subtitles for something with no picture
It sounds odd until you need it: a podcast that's also going out as video, a radio interview someone is cutting to images, a talk recorded on audio only that gets a still frame behind it. In all of those, what exists is a sound file and what's needed is an SRT.
The result is the same as if there had been video, because the timings come from the audio and not from the picture. When you edit later, the subtitles line up on their own as long as the audio hasn't been trimmed along the way.