Padlocks don't prevent this at all. Take a zippered bag (any zippered bag). Jab a ballpoint pen between the zippers, then easily pull them apart with your hands

Padlocks don't prevent this at all. Take a zippered bag (any zippered bag). Jab a ballpoint pen between the zippers, then easily pull them apart with your hands. To re-zip, take the locked-together pair of zips and slide them back and forth from one side of the bag to the other. This requires no more effort or skill than opening an un-"locked" bag.