What is it about vending machines?

Yesterday we were running a bit behind schedule in leaving for swim practice. So, on the way, I said to Nate:
"We're running a bit late, so you'll have to be extra quick in the locker room."

Nate's response:
"Am I going to be late?"

Me:
"No, you just won't have as much time to change as you normally do."

Nate:
"Well, I normally have enough time to get a bar out of the vending machine, and eat it all, and then change."

Me:
"Have you ever actually done that?"

Nate:
"No, but I could if you gave me some money."