Learning how to set all of that up is a massive barrier to entry for the technically average or below-average person. With a modern phone, all you have to do is turn it on and you're good to go.

There are lots of people that you can simply ask and are often willing to help (for example at hacker spaces or maker spaces).

Let's say you're an unemployed single mother, struggling on public programs, looking for work, occasionally selling food stamps to handle emergencies. You worry about how you're going to afford to commute to work before your first paycheck comes in if you CAN find a job, but you can't find a job because your Internet access is so limited, potential employers turn you away because they can tell exactly what your situation is the moment you step in the door (Maybe your shower stopped working, or you've been sleeping on a friend's floor, you can't afford to get your hair done, you only have one old and badly-fitting "interview outfit," you're out of breath after running from the nearest bus stop).

But now you're supposed to go and spend $110+ on a Rasberry Pi and some computer equipment, and find a local hacker space full of rich white dudes and hope that they help you set it up rather than awkwardly avoiding you and quietly wondering how you got in? Class, race, and educational barriers aren't imaginary things that can be solved by the "maker spaces" with friendly utopian facades. In my experience, they're extremely judgmental, fad-driven, and can be overwhelming and demoralizing for those without basic technical knowledge or who don't check at least a few of the "are you one of us?" boxes.

Sure, there are a lot of old people at these meetups and maker spaces, sure there are a lot of women, sure there are a lot of ethnic minorities, people with kids, poor people, people with extremely unprivileged backgrounds, people who don't wear the typical "t-shirt jeans/khakis" uniform, and a lot of people who are just starting out and learning. But you start piling on too many of these "minority statuses" at once, and all of a sudden, it's a very different experience. Even if someone DID have the ability and knowledge to pull this plan together (I mean, I have a master's in software engineering and have been programming professionally for 10 years, but even I would have to do some serious Googling to set up a Rasberry Pi with my TV), why would they willingly put themselves in a potentially ostracizing and embarrassing situation? Very few people want to be the odd one out, or be the subject of speculation, or have their skills and worth questioned while they're in unfamiliar territory, outside of their comfort zone. Questioning why poor people aren't "taking advantage" of these opportunities that are so clearly available to you is just contributing to the problem.

So these lower income people are expected to a: know there's low cost ARM devices that can use their HDMI TV as an input, b: know hackerspaces exist and think they aren't for "hackers", c: walk in to one and say "set this up for me"?

That's highly, incredibly, improbable. Anyone meeting such criteria probably always got a device.

I know low-income people (living from unemployment benefits) who meet these criteria (thus surely not "highly, incredibly, improbable"). The example with the hacker space was just one illuminating example (though I don't consider it as strange: In the city where I live the hacker space organized some public technology tinkering project in the past). There are of course lots of other ways how you can find people who can explain how to set one up.

And have you given them an rpi yet?

For some I set up one, some prefer other ways to access the internet (for example a used computer that they got cheaply from who-knows-where).

I just gave the RPi as one example of a cheap example of a non-mobile-device for accessing the internet - there are of course lots of other ways, too.