I think this is finally being corrected, but for decades kids have been taught "whole word reading" rather than phonics. The basic idea is that instead of learning how to sound out words, they should look at the first letter and guess what they think the word might be based on context/pictures. The proponents of this method claim kids will memorize words as "whole words" and eventually be able to read.
So, they can't actually read. But they know how to look like they can read.
When you can't read it's not enjoyable, so you read less. When you read less you come across fewer words, which you don't really know how to decode anyway because you were never taught.
Anyway these kids are now adults, and even the ones who are smart still struggle with spelling and reading.
Check out the podcast Sold a Story, really interesting investigation on this topic.
There are people who don't have an inner monologue, they just think in abstraction. I have a friend who is like this. She tried to explain it to me and I just couldn't even comprehend what a paradigm shift it is from how I thought all brains at a basic level worked.
It's like when I learned that some people actually see images when they "picture something in your mind's eye." Had no idea that was literal.