Some do have smartphones, but not the expensive flagship models you describe. Smart phones are dirt cheap these days. You can get a new smartphone for $20-50 through a pay as you go carrier. See: https://www.cricketwireless.com/cell-phones/smartphones
Being homeless doesn’t mean have zero money and zero income. Sure there are plenty that don’t have money, but also plenty who get a little bit of income from under the table jobs here and there as they can. Or even those who work part time, but just don’t make enough to save for a down payment and monthly rent payments. But it’s more that’s possible to scrape together $50 to get a cheap smartphone and a one month pay as you data plan. Smartphones are proper computers and can provide access to email, banking, and support services.
I have a homeless relative, my most consistent method for contacting him has been through Facebook messenger of all things. This is one of the reasons that, despite my strong distaste for Facebook, I won’t delete my account.
