One of the more frustrating features of Android is the lock screen voice trigger. It seems that no matter how many times I’ve enabled this, it stops working.
The crux of the issue is that it creates an inconsistent user experience. For hands free and voice interactions, consistency is golden. Whenever a user starts to second guess the interaction, it starts to increase the cognitive load and wear down their patience.
Happy user = consistent responses to requests. Areas of delight are when something works better than expected — like getting a trigger to work even further away.