well, some do, but it is because they don't know any better. but as far as dentists, you will find that many dentists who put in mercury fillings will not get them in their mouths and will not allow them in their family. i remember hearing how the board members at phillip morris said no one smoked on the board because they knew of the health dangers, a board member said that right on tv!
mostly people without a lot of money have to get mercury and don't have a choice. the government cannot relate to those people and don't care what they do as long as they pay taxes and don't cause any problems