Choice and Blame
Among the ideological backgrounds that have planted the idea in people's minds that people are poor because of their personal choices, there's economic theories like this gem.
"Landlords, monopolists and other vest interests defend their privilege to charge what 'the market' will bear by denying that there is any such thing as unearned income.... Rentier income and wealth is supposed to 'reward' its beneficiaries in proportion to what they are assumed to contribute to the economy's output. This is the economic theory of John Bates Clark and his followers. It assumes that everyone earns whatever income and wealth they manage to obtain, regardless of how they do this.... To cap matter, any transaction is said to be a voluntary exercise in choice by definition -- even borrowing to avoid starvation, or sleeping under a bridge." (Michael Hudson, "Methodology is Ideology, and Implies Policy." J is for Junk Economics, p295)
When every outcome is the result of personal choices, you wind up saying crazy things like Margret Thatcher's line, "there's no such thing as society." And you believe crazy things like, "people are poor or homeless because they want to be." Or equally crazy things like, "I'm rich because I chose to be."
Choice is a real thing, of course, and plays a role in personal outcomes. Sociologists talk about it in terms of agent based and structural based forces. But never underestimate how much choices are shaped and constrained by context.