Not only can any suitcase lock be opened by a $3 bolt cutter as noted by the above posted, but for soft-sided luggage, most zippers can be opened with a ballpoint pen or similar. Even a hard-sided bag can be forced open if someone really wanted inside. The only reason to lock a suitcase is to guard against accidental opening if caught on a piece of equipment, etc.

You can't be serious about someone putting radioactive material or other contraband in your bag? Smugglers aren't going to place valuable items in a random stranger's bag - they have mules hired to do that!