Not all but many airports treat baggage reclaim from domestic flights differently than international flights. Again there are exceptions such as Atlanta and a few other U.S. airports for instance. There, once you have completed the immigration and customs process and your final destination is Atlanta, your suitcase will be taken away from you and travel separately for collection at the main terminal. This is so that passengers don't clutter the terminal transit system with all their baggage. Consequently, although you arrived on an international flight, your suitcase will now arrive on a belt completely accessible to the public. They at one time did tag checks, but that is no longer the case.