Why is Hermes' symbol used by some doctors?

firstly, who am i to judge the fact you think your the son of hermes, secondly, i think it was used because it made people believe in the fact that there were two options in medication, life or death evidently, even though that may not have been its original intention, the two snakes heads work perfectly in symbolizing this as a snake can either choose to bite you and it will kill you, or it can be stopped from death, so wether its right or wrong to do so they will continue to use it i suppose...