Sometimes it’s just bad parts from a supplier that only affects a tiny amount of vehicles sold.

I had a motorcycle with a front tire recall. I actually had to take it to the dealer for them to check the tire itself. They had two different manufacturing batches of the tires in the motorcycle manufacturing facility at the same time. One batch was bad. They knew the VIN’s of the bikes that could be affected but had no way of knowing which batch of tire went on what VINs. They had to send recall notices to the whole range and check it out individually knowing only about half of the VINs notified actually had the problem. Plenty of bikes made before and after the bad tire batch that weren’t in scope of the recall.