Probably because they don't have much leverage in this area, with Biden continuing some of Trumps policies on tariffs.
Targeted tariffs as part of a trade war is significantly different than the proposed universal tariffs to "eliminate taxes" that he's proposed.
AKA: we figured out how to pass a consumption tax which disproportionately hurts poor people without calling it that because we know it's universally unpopular. When billionaires effective tax rate drops to what will probably be 1%, the wheels are going to REALLY fall off.