If you’re talking about aphantasia that’s less than 5% of the population, not half
Approximately 30% to 50% of people regularly experience an inner monologue, while the remaining 50% to 70% do not have a talkative brain.
https://www.bustle.com/wellness/does-everyone-have-an-internal-monologue
https://science.howstuffworks.com/life/inside-the-mind/human-brain/inner-voice.htm