Those are the most likely. Another factor, less common, is when you want or have to speak a non-native language you're not used to pronounce, in which case you

Those are the most likely. Another factor, less common, is when you want or have to speak a non-native language you're not used to pronounce, in which case you're usually afraid of not being understood. PS: I think all the Text To Speech systems sounds horrible, the last generations are even irritating, as the user of the parent commented.