They're demonstrably bad rules. You know how when kids first hear about tax brackets and misunderstand them to mean that someone earning near the top of one br

They're demonstrably bad rules. You know how when kids first hear about tax brackets and misunderstand them to mean that someone earning near the top of one bracket could get a raise of $x and end up having their tax bill increase by more than $x? We don't do that because it's universally agreed to be a bad system: it encourages you to stay poor. Instead of diminishing returns for more work, you get negative returns for more work. Luckily, our tax system is (relatively) sane and uses marginal tax brackets to avoid this outcome. The SSI policy does not—it has this exact failure mode.