Why do nurses take the fall?

I'm a nurse tech at a hospital and we do the vitals, I&O's, chart, general patient care ya know. So why is it when a patient hits the floor, I&O's/vitals don't get done and or charted, there is inaccurate charting, or whatever else the tech was hired and responsible to do, the nures takes the heat from the doctor and or manager? I don't get why they can hire us to do the job but ultimately the nurse carries full responsibility of the patients. I personally want to know if I'm doing a good job or if there are things I can work on. In order to know these things i need to know when I might have accidently screwd up. So if they can hire us to do the job we should be responsible for the job we do.... Why aren't we???