Another advantage is that a metre is a metre everywhere, and a litre is a litre everywhere (spelling notwithstanding.) A lot of the imperial units are regional

Another advantage is that a metre is a metre everywhere, and a litre is a litre everywhere (spelling notwithstanding.) A lot of the imperial units are regional. A tablespoon may be either three or four teaspoons. Who knows how much a fluid ounce is. One very real PITA is reading cooking recipes and having to do some deduction to figure out how much the units actually are.