Zippers on bags and backpacks

The zips on bags and rucksacks can be opened on the right-handed side - left-handed people carry the bag/rucksack (when opening) on the right shoulder, i.e. the zip is on the back. You can't open or close it without contortion and corresponding flexibility. A simple solution would be to equip every bag, every backpack with zippers that have TWO zippers!