Eh, it isn’t all the time for most people, and it isn’t hard to shut down for most people either.
The key is that it isn’t a separate entity, it’s just your own mind using words to ideate. Like, you can see the sky and just enjoy the blue, or you can think about the blue in words, if you have that inner voice. People without that voice still have a way of processing and thinking, it just isn’t in words, it’s more abstract.
The few people I’ve met that don’t think in words do seem to have difficulty in expressing the experience to others though.