The walls in long streets of housing, like down here in Portsmouth, are not on insulated, but designed to be fire resistant.
Plus don't underestimate the value of using a material (bricks) that isn't actually fucking flammable.
Also semi detached houses typically don't have this, and do share loft spaces separated by a thin wall, but usually the fire brigade is called before both houses go up in flames
Actually, no. Those wouldn't be a fire hazard as houses in the UK are not made from plywood and prefab materials (at least not the ones in those pictures) like American ones. They're old school full-brick houses. The Great Fire of London was precisely due to houses being build with a predominance of wood and people keeping large amounts of kindle and firewood on hand for heating.
Plus don't underestimate the value of using a material (bricks) that isn't actually fucking flammable.