Why don't they listen

So I went to get lab work today and I told the tech that no one ever has luck getting blood from my arms and they always have the best luck on my right hand.

Well she didn't listen. She tried both arms and couldn't find a vein. Two painful sticks. So she got another tech. The tried my left arm and fail so I again politely asked them to please try my right hand. So he finally did and they got a vein on the first try.

I don't know why they don't listen. I've only lived in my body my whole life so I'm pretty sure I know what I'm talking about.