Why? For the same reason we have personal bankruptcy laws at all. Sometimes people have misfortunes of one kind or another and need a second chance at life, without the burden of large debts.
I paid my own student loan, which was small, and my children are paying theirs. But sometimes people can’t pay.`
Yes, people have misfortunes sometimes but they all didn’t have a misfortune. When that state cut off their driver’s license or nurse’s license and all of a sudden 98% of them started paying again - that tells me a lot!