There are lots of old guitars around. Some have survived despite the neglect, and many have probably ended up in the dump or as kindling. I know of a fellow here in Boise who has a garage full of nice old ukulele, including Kamaka and Martins. He has never made any attempt to heat or humidify and some of them are not even cased, so almost all of them have terrible cracks and other damage. He just brushes it off as, "they all do that". So true, when they are abused. Some people should not be allowed to have nice instruments (or pets, or children.... but that is a whole 'nother discussion).
There is a certain amount of luck involved too. If the guitar lived in grandma's attic, it probably died. But if it lived under the bed in its case in a home (where the people were reasonably comfortable) it may get away unscathed. I have also recently seen old timers with Martin guitars that they bought new in the 1930's but were prized possessions, and treated accordingly. One 00-18 even had the original pickguard worn through, with a corresponding hole in the top underneath.