In a galaxy with so many species, each with their own physiologies and illnesses, medical droids ensure relevant emergency treatment and basic care is always available. Capable of everything from simple diagnosis to complex surgeries, medical droids are common on starships, frontier colonies, and other places where highly trained medical personnel are in short supply. Due to the importance of experience in medical practice, these droids rarely have their memory wiped as other droids do, except in cases of damage or malfunction

~ Source: Star Wars: The Old Republic Encyclopedia