Because it buys votes for Democrats.
Because our young are our future?
The ONLY reason this would ever be considered. I noted years ago that in due time Democrats will seriously propose this. I predict that as Hillary will be the nominee, she will fail to connect with the young the way Obama did. Hillary will be a dud to the Millennials. Therefore, Hillary will propose a waving of the magic wand and eliminating this debt. Oh sure, there will be some ridiculous smoke and mirrors plan that goes with it, but it will absolve all their debt, to be paid be taxpayers, i.e., Republicans.