Nothing in the tech world is ever absolutely perfect. This is like saying that you'd never use any app that ever had a possibility of crashing ... and there aren't any of those out there.
Of course voice control will never be absolutely perfect, but it can be vastly improved though. I can talk much faster than I can type, but AFAIK there is currently no voice recognition software out there that will transcribe me reading a passage aloud at my normal speaking speed without getting a load of errors.
FYI I do use voice control for my telephone banking, works quite reliably in Mandarin Chinese and I'm not even a native speaker. But it's only got to recognise numbers though, a very limited vocabulary.
It's rather like handwriting recognition, they've been at it for decades, but it is still in its relative infancy. Printing might be OK, but it can have serious problems recognising normal cursive/joined-up writing.
The other problem with things like Siri and similar, is that they have to be connected to the internet for them to work. My old Nokia E71 smart phone had voice dialling and control which didn't need the internet, but I never used it, as it was so unreliable.