I do, do you? Microphone sharing (a) means only one person at a time can access it and (b) it is way more inconvenient. Microphone creators are not threatened by sharing, digital creators are.
If someone steals 20 microphones from the mic creator he has 20 microphones less. If someone downloads 20 songs from a song creator the creator of that song still has the song.
In fact I can chip in and share it with 200 friends if I want to.
You see the difference?