I assume some people decide to use
+++ YouTube Music +++ as a streaming music source. If so, then their music source is videos.
If someone decides to stream
+++ Pandora +++,
+++ Spotify +++,
+++ SoundCloud +++,
+++ Apple Music +++ or any streaming service not mentioned as a streaming music source, then their music source is audio.
There is a lot more audio streaming music sources than video.