It was added in API 15 (4.0.3), which would cut out 36% of the current user base if the minimum was set to that. I'm not ready to make that sacrifice. If there becomes a reason to (optionally) use the extra callbacks, UtteranceProgressListener can be used for 15+ and OnUtteranceCompletedListener for <15. Until then, I'll just stick with the old listener to keep things simple.