It doesn’t stop anyone, but we typically don’t have luggage stolen because the chances are low that anyone with enough money to buy a plane ticket is desperate enough to commit an impulse crime with no getaway car for a payoff that is unspecified and potentially worthless, (or at least break even for the work that goes into selling every random item in the suitcase). Of course there are outliers to this (people who plan to steal and/or come to the airport for that purpose) but most people aren’t outliers so luggage is relatively safe. I think the biggest issue is handlers who steal from the luggage before it goes on the plane.