If you would like the judges to rate them, then they may. They are allowed to keep it disclosed if they desire or reveal it as well if you ask for it.
I perceive judges as the ones viewing the work, critiquing, find its selling point, what may be improved, how it appeals...
They help the rest of the voters to decide by reading the judges' comments... The voters have their own personal reasons for voting a certain individual... but a change of perspective like from the judges may aid them in the process.
Each judge votes who they like best and they'll be incorporated with the rest of the votes.