Personally, I remember Google telling me that they "may use recordings to improve the voice recognition quality" or something like that. What I did not realize is that that meant humans would be listening. Sure, any ML expert will say "Well obviously! A machine can't train itself!", and in retrospect I wonder why this was not obvious to me. But here I am, a software engineer who worked for Google for eight years, and it was not obvious to me, somehow.
These services need to state more clearly how data is being used. When you sign up, it needs to say, clearly: "Human employees of [company] may listen to your recordings for the purpose of improving voice recognition."
I think the reason we are not presented with such clear language is because the people building these products know they'll lose a lot of users. But that's no excuse to mislead people.