I think there is a reason to keep audio and video playback separate, because you approach them differently.
When you are watching video, it's usually where your attention goes, whereas listening to audio is something done "in the background", while your attention is elsewhere (reading, writing, playing a game, or even cleaning the house).
Therefore to me it is obvious that an audio playing application should behave like a good butler - readily available when you need to e.g. change the playlist, but invisible otherwise - and I would compare a video playing application to a live entertainer.
A video playing application should of course also get out of your way so you can focus on the actual video, but there is a subtle difference nevertheless.
When you are watching video, it's usually where your attention goes, whereas listening to audio is something done "in the background", while your attention is elsewhere (reading, writing, playing a game, or even cleaning the house).
Therefore to me it is obvious that an audio playing application should behave like a good butler - readily available when you need to e.g. change the playlist, but invisible otherwise - and I would compare a video playing application to a live entertainer.
A video playing application should of course also get out of your way so you can focus on the actual video, but there is a subtle difference nevertheless.