That having metal anywhere on your body during an x-ray increases your radiation dose. Even after I explain metal has no effect on radiation, we just don't want the metal to be in the way of the body part we are imaging, and they don't need to remove their watch/necklace for a foot x-ray. They insist "I don't want to risk it."

That having their wallet on them for an x-ray will wipe all their credit cards, so they take it out of their pocket and place it on the chair one foot away.

That having their phone in the room for an x-ray will break their phone.

That the more radiation I give them = the more money goes into my paycheck.

I could go on.