I suspect that the only pizza boxes that strictly need it are the largest size boxes which are considerably rarer in the UK. For instance the largest size pizza

I suspect that the only pizza boxes that strictly need it are the largest size boxes which are considerably rarer in the UK. For instance the largest size pizza at domino’s uk is 14.5 inches in diameter compared to 16 inches in their US locations. I also think that the corporate chains that are pretty popular here in the uk have reinforced boxes with corners that fold in.