Somebody Get This Man A Microwave

Today I answered the phone at the restaurant a few minutes after the lunch rush finally dwindled down. An elderly old man on the other end sounded pleasant enough, and that's precisely how I knew I was in for something bad. Here's the gem of a conversation that followed:

Me: Hello, how may I help you?
Old Guy: Yes, hello. I was just in your restaurant picking up a few slices of pizza about 20 minutes ago, I'm sure you remember me. (Yes clearly, because the line of customers wasn't out the door and the phone wasn't ringing off the hook at the time either. I had more than ample time to commit your name, voice and face to memory)
Me: Oh....
Old Guy: Well, it's just that I wanted to call back and tell you that when I got home, the slices were cold. I didn't think you left them in the oven long enough when I was there, and I almost asked you if they were ready but I didn't. You didn't cook them all the way (They're precooked) and they were hot on the surface but ice cold in the center. You know if you don't heat something up long enough it's cold. (No, really? Is that really what happens? I guess I should have watched more Bill Nye The Science Guy when I was a kid). My wife was very upset and she said it was the worst pizza she's ever had.
Me: Oh, I'm really sorry to hear that sir. Would you like me to credit your account with the cost of the slices?
Old Guy: Oh no, that's okay. I just wanted to tell you because if no one did then you would be giving lots of people cold pizza and I'm sure a lot of those people wouldn't come back.
Me: Well, I appreciate the heads up. Thank you.

I cannot figure out, for the life of me, what type of person in the 21st century (land of microwaves and ovens) CONTINUES to eat a slice of cold pizza, when they could EASILY place it in some kind of heating device, wait a few minutes and then they could have the hot pizza they so desperately desire?

Also, how is this at all my fault? I just take your effing order. Do not call me back and give me a 5 minute lesson on the thermodynamics of your $1.75 pizza slice. Get off your soapbox, utilize a few brain cells and maybe figure out how to work that gosh-darn, newfangled microwave device of yours.

They don't pay me enough for this.