Stealing from luggage has been a problem for the airlines since they first started carrying people in planes.
That said, LAX has always been a hotbed of it.
Some of it because you have many airlines with only one or two flights a day using contracted employees, to baggage belts that are easy to steal bags from, and get to a car quickly.
I fly out of LAX. Before I fly I pack a box of clothes and mail them where I am going. I board with a carry on.