the aforementioned reasons are good ones, but another that should be mentioned is that if you're going to blow a half trillion (or more) of new spending at something that builds nothing, produces nothing, creates nothing of public use, directing that money at the richest segment of society rather people living more challenged lives is obscene.
firstly, i agree w/ everyone that this is just treating the symptom and not the underlying problem. College has gotten un-necessarily expensive and for no other reason than greed. And when the free market won't bear it, rather than reduce the price like that good old invisible hand would mandate, instead they put their thumb on the scales and come up with new and exciting ways of making it easier for 18 year old kids to have access to predatory loans that they almost assuredly don't fully understand of which the vast majority of them will not be able to make their payments in full, on time, and on schedule.
i think its a bit of a stretch to classify the people who would be receiving this debt forgiveness as "the richest segment of society" The eligible persons for this forgiveness are predominantly middle/slightly upper middle class people who are fairly new to the workforce and relatively low earners - at least as far as full time/salaried workers go.
I don't think its fair to just say it "produces nothing" because the fact is when people who are living paycheck to paycheck and then they suddenly have an influx of cash - as in, a no longer having to pay an otherwise recurring payment - they always always always put it right back in to the local economy, because that makes sense right? You don't have the luxury of just setting aside lots of money to save it for a rainy day, so you spend on stuff that you need. Most likely the people living paycheck to paycheck are not able to take care of all of their needs, so that extra money will allow them to do so. It is only the rich that horde their money, which they absolutely unequivocally do, without fail.
So of that $30B a year, just about all of it is going to get pumped right back into the economy instead of just lining the pockets of the already super wealthy.
fwiw i also agree with you in the sense that if we are just going to be spending $30B a year i would much rather see it go to the poorest people that need it the most, but that's an even tougher sell to the american people unfortunately because we really hate poor people and really hate doing anything to help them or make their lives even slightly less miserable. All i'm saying is its not like that $30B every year is just getting lit on fire, it actually will legitimately "trickle down" as you Reaganites like to say.