I think you are misunderstanding what people mean by "cancelling debt". They don't mean they will force lenders to suffer a loss, they mean that government will cover the debt.
If the gov actually decided that the current situation is not sustainable and it's better for everyone to cut the losses and cover everything... why would it guarantee another loan like that the next day?
The companies themselves could be interested in that loans of course, but without the previous guarantee the risk would be too high.
What you say makes sense, but the people proposing student loan cancellation do not talk about rolling back government guarantees on student loans. If they did, that would be totally different discussion.
Many do not, mainly concentrating on the post-covid impact. But at least two links from this article talk about limiting the ability for student debt collection, which would significantly limit the number and/or size of the student loans given.
The companies themselves could be interested in that loans of course, but without the previous guarantee the risk would be too high.