Not because of its cost. Not because it is unfair to those who pay off their loans

But because it is UNCONSTITUTIONAL.
2)

The President of the USA cannot make law. The President of the USA cannot usurp the responsibility of the House of Representatives which under the US Constitution is the sole body that can allocate Federal Funds.
3)

In any case, this plan, floated by Biden just before the Mid-Term election, was a cynical effort to manipulate the vote - to get young people to vote. I cannot believe that the Administration is stupid enough to think this cynical plan would pass legal scrutiny. 4)

This was just like the illegal draining of the Strategic Oil reserve, endangering American Security in violation of Federal law, again manipulating the vote by lowering fuel costs temporarily. 5)

I would not oppose a plan to forgive Student Loans about which there was never going to be any hope of collecting - retired people without income, disabled people, etc. That would also cost the Treasury nothing. If you can’t collect anyway, why waste the paperwork." 6)