What's predatory about public loans. They all qualify for income based repayment, which means you'll never pay more than 10% of your disposable income (any income over 1.5x the federal poverty level). If you make below that amount, you'll never be required to pay back anything. And they are cancelled after 20 years.
Theoretically you'd owe tax on cancelled debt, but only up to the point of solvency. And a borrower who hasn't made enough income to pay back a student loan after 20 years probably isn't solvent, so won't pay anything. This also assumes that as more and more people reach this point, there isn't demand for congress to change the tax code.
Public loans make up about 92% of all student loan debt as well, so the vast majority of loans are going to qualify.