Because making it universal is cheaper. If you set the cutoff threshold high, then you're barely saving any money and end up spending a lot more on the bureauc

Because making it universal is cheaper. If you set the cutoff threshold high, then you're barely saving any money and end up spending a lot more on the bureaucracy than you'd save. On the flip side, if it's anywhere close to the income of a middle-class person then you could get an effect where earning more money makes you worse off. Of course you can taper it off instead of making it a sudden cut-off, but that makes the bureaucracy even bigger.