ive talked to plenty of nurses who were never trained to switch the needle off the syringe after drawing from the vial. but after seeing the pictures of the needle through a microscope after each use, you can see the rapid degradation of the needle. I prefer to do as little damage to the inside of my body as possible. Besides most people getting a shot from a nurse arent getting a shot ED or EoD, I get a shot from the doc like once a year tops, for the flu or maybe a cortisone shot every once in a while, i could care less if they dont switch the needle. but when i have to pin in that same spot once a week I'd like to use a clean sharp needle so that there is less of a healing process and less scar tissue build up overtime.