Why would somebody steal Galileo's fingers? Here is the answer from Bruce Hood (his fantastically reviewed book, SuperSense is on my reading list):
Here is the original link.
People venerate the mortal remains of the dead. If you think about ritualistic funeral practices around the world, most cultures (but not all) treat the corpse with dignity. Paradoxically, people who believe in the soul and spirits are also inclined to believe in the supernatural “essence” of body parts and bones.
As far as the recent theft is concerned, I don’t think that there is anything intrinsically important about Galileo’s fingers other than the fact that one of his fingers had previously been removed and made into a relic that is currently on display in the Museum of the History of Science in Florence. Another finger relic that seems more appropriate is St. Thomas’ doubting finger, that St. Helena allegedly brought to Rome from Jerusalem, housed in the Chiesa di Santa Croce. Otherwise, people value material objects (sports memorabilia) that have an intimate connection with those they venerate, and what could be more intimate than a body part?