Not entirely. The environment pharmacists and technicians work in is stressful. The pharmacist often works 12-14 hours a day, with no real break, no meal break, and he or she is often supervising four technicians who don't have the educational background or expertise of a pharmacist. Techs work 12 hour days and longer, and are paid much less, often barely above minimum wage.
Busy and stressful environments combined with tiredness contribute significantly to the problem. Humans make more errors when they are tired and hungry, but being tired and hungry does not relieve or excuse them from their duty to the patient.