It is definitely a shame....but in most cases I think the owners just won't part with them, I guess mostly for sentimental reasons, or coz they think it will be worth something oneday, even tho oneday they'll realise it won't be worth anything coz she's to far gone from sitting around.
I know a guy who bought a red VH SS 253 4spd brand new off the show room floor. Ever since I've known him (maybe around 10 years) it's been sitting out the side of his house under the veranda, with crap stored around it, on it, and dust and crud all over it. I always use to keep asking him about it, but he just laughed everytime.