Literacy is the wrong word to use here. It doesn't work to compare English literacy with this sort of thing.
English literacy in school is gained by a lot of practice. Writing, even if it's texting friends, is something you do daily and throughout the day. The written language is in the same language (though there is some transformation involved in turning words in the brain to symbols on paper) in which you think and speak.
Doing something like computer programming is far different. You won't get daily practice just by going through the norms of life. Even pushing yourself to getting daily practice won't happen if you don't have something on your plate which is interesting. People are lazy by default and just opening an editor can be too much effort. I procrastinate bad enough on paid projects, let alone things nobody is expecting me to do.
Just because people can read, doesn't mean they pick up books to better themselves. People would much rather be spoon-fed entertainment through TV.
I don't see the point of learning to code beyond having some familiarity with it. For this to be a useful skill you have to put a huge effort into keeping up with it. Learning a different language is a huge barrier (not difficult, but for surpasses the point of which most people are willing to go.)
Jobs aren't easy to land. There is no equivalent to manufacturing in tech which can lead to an army of workers being employed. The tech rabbit hole grows deeper each day as we add more tools and specialty areas in which we need to be familiar with. Areas such as wrangling data has a daunting list of pre-reqs and I imagine this will be a trend moving forward (programming paired with knowledge of the domain you are building software for.)o
The sad fact is that technical knowledge doesn't take down the issues which data shows to be a problem with people in ghettos.
People who live in a ghetto have a hard time moving. A life of poverty creates huge issues which people who don't live in poverty don't understand. It's called grinding poverty for a reason. The grinding is going on in your head and that will drive you mad. For a long list of reasons, jumping past the most bottom rung of the employment latter is something few people in this situation will ever be able to do. A well paid programming job isn't a bottom rung job.
Well paid development jobs are well paid because they are hard to get and hard to employ for. If it were easy, then they wouldn't be well paid. Teaching people in the ghetto how to write code isn't going to help them get these jobs and it isn't going to help employers in hiring.
Freelancing and the gig economy is even worse. You can make far more money going solo by starting your own shop than by traditional employment. But the same ratios work here as in the rest of the economy. You get 1% (or less) who can figure out the game and thrive while everyone else just scrapes by.