Shouldn't they? Lots of people have feet different sizes. Some people only have one foot. My right foot is badly swollen due to injury so my options are: wear a shoe far too small for my right foot (painful and bad for it), wear a shoe far too big for my left foot (so my foot flops around in the shoe making walking awkward), or buy two pairs, one in size (expensive and wasteful). Wouldn't it be fab if you went into a shop and they asked your size, and you could say "left 7 right 8"?