You mean you used to be able to just send a bag without flying yourself, and have someone else pick it up at the destination airport? Was this something that people did intentionally or did it happen accidentally?
This is false.
If you check into the airport early (4+ hours) your bag may go on an earlier flight without you.
And you can decide not to board your original flight.
But I could be wrong. Maybe it's just rare enough that I haven't run into it. I would expect it would delay the flight by a noticeable amount. And it would be fairly obvious that they're unloading luggage and then reloading it. It's not like they can just send someone in to climb around and find it. They pack them in tight.
Someone told me they'd done that in the 70s. In their case, they were planning to travel and bring along stuff that belonged to a friend at their destination. At the last minute, they couldn't make the trip and they decided the easiest solution was to check the bags and scurry out of the airport. They were worried the airline would deny a refund, but they got their money back just fine.
Baggage claim was no problem. Anybody could (and mostly still can) access it. I remember a time where they kind of corralled it all in and checked your bag tag and stub to make sure you weren't wandering off with someone else's luggage. That was a chaotic, ineffective, and short-lived effort.