Fiance has no common sense..? help!

So my fiancé, he's 24, has zero common sense... He's a smart guy when it comes to certain things, but he doesn't "get-it". I got sick when we first began dating two and half years ago, while camping, because he didn't wash the old griddle before he cooked my food on it. I threw up the whole trip! Every night! We still bring it up often because it's a fond memory of our first camping trip and no hard feelings... But today he seriously did it again. The griddle hadn't been washed from yesterday (there was a get together my mom assembled) and he decided to make hot dogs on the griddle for us today. It was OBVIOUSLY dirty from the day before, and he still cooked on it. He also didn't know hot dogs are pre cooked... I told him this like a year ago and I had to tell him again today. He was like "I want to make sure it's cooked all the way." And when I told him they're pre cooked, he goes " Oh, are they?."