Yes, I have seen this reality a 1000 times and more some. First reason I would say is economics......costs more to fix than it is worth. I try not to look at all repairs from that POV. I personally try to take into account other costs that you incur from a new or newer acquisition...sales taxes, license costs, higher insurance (assuming higher replacement value), and then personal satisfaction of just fixing something and making it last.
Another thing that happens is, by the time a car gets to a second or third owner, they are not as emotionally or economically attached to the vehicle like the earlier owner was. They start to see the car as a problem, a headache, a money pit, something that is always breaking or has become unreliable for the duty it needs to serve them by. Here in the mid-west most yards are not keeping any inventory older than 10 years. Maybe 12 - 15 at the most if it was / is a high volume model.....think Accord, or Camry, Corolla, etc. This changed somewhat during the pandemic when all of the OEMs had parts supply chain issues, and the last 2 years for most organized yard owners, and scrap dealers has been a boom.....however it is starting to slow down.
It will be interesting to see how all of the OEMs will continue to supply or support ICE parts after they make the complete transition to EVs. The common auto dismantler may get a second wind in supplying lots of parts that are simply no longer available from the OEM or aftermarket suppliers.