EDIT: If you feel strongly about this and think it's possible please send in PRs. Thanks!

Unfortunately you then lose ability to play back the original audio https://stackoverflow.com/questions/2319735/voice-recognitio.... This is a major usability tradeoff IMO, though I'm willing to be swayed to add an option.

I suspect Google's limiting this because they don't want devices "freeloading" their cloud transcription service, since most phones can't do it on-device.