why don't high beams don't work

Totally SEPARATE circuit , < maybe 'pushrod' here will chime in and correct me , but I suspect the switch has failed , or it may have a 'lighting control module' in that , which may also be at fault. You have already proven that the bulbs and a large portion of the circuit are working properly! TEST the switch , if you are able. IF it's a cheap enough and easy enough guess for you , that it's worth taking the chance that I'm wrong , throw a switch in it. But I much prefer the 'test and prove' method!!