I most certainly don't intend to be using 'em after I get going, and this way some part of me sticks around to be of help to someone else afterwards. It's sort of like reincarnation on the installment plan. Hell, I wouldn't mind doing that with my whole body instead of just the organs.
Oh sure, it's macabre, but incredibly practical! Not even just for medical purposes! My skull could be a sweets tin, my ribs stick out so much they'd make for a nice filing cabinet, and I'm sure they'd be able to find SOMETHING to do with all this hair... I'd be able to keep making myself useful to my friends and family after the fact. I can think of five people I'd be more helpful to in such a state than now anyway =D