My wife wanted to play Phasmophobia and the mic wouldn’t work because the input was defaulting to the headphones but the output was to my speakers. When I switched the output to the headphones, no audio worked, input or output, at all.
iTunes does this shit too where you have to restart the app to get the audio stream to change.
Why so shitty?
Depends how the software developers implemented their audio functionality (acquiring a direct channel on the audio interface at launch, they should at least have a menu to select an alternative post-initialization). iTunes probably had that because it sets some bits about DRM compatibility, particularly for video content with Fairplay DRM, since it's such an old monolithic codebase I'm sure.
For games, I could see the decision to bypass DirectSound or something higher level where you just pipe the audio to Windows and let it resolve the default output being based on latency or something, most likely inherited from a decision made in the engine that this engine is based on decades earlier.
I don't do much with audio output in my development background, I'm sure it's just a result of requirements, timelines, and developers making something work just to get it out the door and if people aren't concerned with breaking the latency thresholds or DRM compatibility they can install a virtual audio device and set that as default, and have that go the physical interface they want. Virtual Audio Cable for instance, not sure if there's a FOSS/freeware alternative but I've had that cracked for decades.