Exactly the opposite is true. People who make their payments get low interest rates. People who don't, get higher rates. That's the way it works.
Think about cars. Car dealerships know almost anyone coming in the door can get approved, but only if they hold prices down at a reasonable level. Beyond that level, the banks won't loan the money because the loan isn't guaranteed to be paid back. There's no such mechanism in education, because loans can't be discharged and they're guaranteed by the government, so there's no reason for schools to sell their education for a reasonable price.
You misunderstand. If the rules are changed so that fewer people will have to repay, then people will take advantage of that -- and fewer loans will be repayed. This means that the banks lose money. For them to stay in business (or at least to be able to maintain their capitalization -- investors will flee if they can't make profits), they've got to pass those default costs on to the customers. Thus, all of us will pay a higher interest rate to make up the shortfall.
Think about cars. Car dealerships know almost anyone coming in the door can get approved, but only if they hold prices down at a reasonable level. Beyond that level, the banks won't loan the money because the loan isn't guaranteed to be paid back. There's no such mechanism in education, because loans can't be discharged and they're guaranteed by the government, so there's no reason for schools to sell their education for a reasonable price.