I am a writer. I am one of those "destitute people"--even though I have published a book that's sold 40,000 copies in three years, I make far less money than an anverage McDonald's worker.
The answer to your question is that a smartphone is cheaper than a computer, and a computer or similar device is the cost of entry into modern society. It is nearly impossible to function without one. That means when you're poor, you prioritize your smartphone sometimes above food, because the consequences of not having a smartphone are likely to be more severe for you than the consequences of skipping a meal.
When you're middle class, a smartphone is a luxury. When you're poor, it's a necessity. More and more government and social services rely on Internet forms. Jobs are increasingly applied for online. Sure, if you're lucky enough to live in the right place, you can go to the library and use their Internet to fill out your forms, and maybe set up a free email on Gmail, but without a phone, how do they contact you? And when you're poor, transportation can be expensive and extremely time consuming. If they need a new form, you can waste half the day taking the number 28 bus to the number 67 bus and transferring from there to the number 3 express that drops you off a fifteen-minute walk from the library so you can use their Internet, but good luck doing that if you're working three 20-hour-a-week jobs like many poor people do, or you have a kid to take care of, or both.
And yes, an iPhone 7 Plus on Verizon is expensive. A secondhand iPhone 5C with a chipped screen that you got from your sister-in-law and have a minimal data plan for is not.Landfill Android is even cheaper. (I have an old iPhone 6 with a defective battery; I could get the battery replaced for $100, but I haven't been able to yet. I am on a Canadian voice and data plan that costs about $35 a month and gives me free roaming and voice and data in the US. Americans routinely pay 3-4 times more money for their cell phone plans than the rest of the world; when I was on Verizon, I had European and Canadian friends flat-out refuse to believe me when I told them how much money the normal Verizon plan cost and what it got you.)
I've been well off. I've been poor. One of my experiences is that people who haven't been poor have no idea what it's like, and so are prone to judging the choices you make without any understanding of why you make them, even though they've never walked that mile in your shoes.
When you are poor, you become a master at prioritization and making tough choices. I recommend having faith in people's ability to make those choices, rather than armchair quarterbacking them from a position of ignorance.
