Well, yes there have always been thieves, but now the security procedures preclude the use of locks!
I recently flew across the country with a handgun in my checked bag. The handgun was in a locked gun case and the piece of luggage it was in was locked. I used a TSA lock, see an example at http://www.tsalocks.com/ , so that I would know if the bag had been disturbed. I had absolutely no problems the entire trip.