When did they stop the unattended baggage warnings at airports?

In the past, if you were flying through any airport in the United States, you could expect to hear a recorded announcement every 15 (?) minutes about how you can't accept bags from anyone, and unattended baggage may be damaged or destroyed. I'm just wrapping up a trip now, and I haven't heard any of those announcements. They were obnoxious, but they were a part of the airport experience. Do any of you know when they stopped?