It's a real pain—let's just start there. Lots of people hate needles or are outright afraid of them, and that's reasonable enough. Very few people want a stranger to poke them in the arm with something sharp. Sometimes you even get fatigue, or aches in your muscles. Then, to add insult to injury, you sometimes end up coming down with the flu anyway. What was even the point? And they want you to do this every year? Voluntarily?