“Why are these companies exempt?”
An essential hallmark, and foundational lever to power among the venal criminality that is Marxism.
I think this whole thing is a backdoor bailout of the American Government.
Insurance companies hold most of their money in Government bonds.
US Government agrees to make every American pay those insurance companies and act as the collector through the IRS.
Insurance companies agree to put a healthy portion of their collections into US Government bonds since demand is on the decline for them through the existing market.