In the 1970’s and 1980’s there were several books the either had characters that did it or promoted it.
Why is there no cooking tray in my new car’s engine bay?
Is it dangerous? (It would be less physically dangerous if there was a specific spot for it.)
In the 70’s fuel was cheap.
Nowadays, if I need to let the engine run for an hour, I can go to a michelin star restaurant for the same price. (OK it’s an over statement, but there is definitely cheaper and more optimal way to cook a meal on the road)