They absolutely wouldn’t because the US has one of the most regressive subsidies on mortgages in the world. But! Banks don’t (usually) hold mortgages. They sell

They absolutely wouldn’t because the US has one of the most regressive subsidies on mortgages in the world. But! Banks don’t (usually) hold mortgages. They sell them to Fannie/Freddie the actual agents responsible for the regressive tax. So banks will have mortgage exposure in the form of mbs, but those are not structured to be extremely long dated.