Because good old Bill KNOWS he will be fired by ultimatum boy if he recuses himself from anything the orangehead doesn't want him to do which is EVERYTHING THAT AFFECTS HIM. Barr talks big and sounds sincere and has hit quite a few "right notes" and yet he refuses to commit to the most important thing which is that he is completely entirely and absolutely INDEPENDENT of the president and will ALWAYS DO THE RIGHT THING and not the ultimatum boy demand/command if it is the WRONG THING TO DO.