There are some people who think it is somehow safer to store a bolt action with the bolt removed.
It is "safer" if no one knows where the bolt is stored, but then again, so what?? From a safety perspective, guns don't, and can't get any "safer" than unloaded.
Some people take the bolts out, (or other parts) not for just safety, but as an added security measure.
Without the bolt (or other vital and obvious part(s) ) you can't use the gun. A gun with obvious parts missing is of little value, and even a dope head knows that much, and won't bother taking it, in favor of things worth more money.
No, its not a fool proof solution, as there are more than enough fools to go around, but generally speaking, anyone stealing a gun, is doing so in order to use it, (in other crimes) or to sell it, and the people buying stolen guns, either for their own use of further resale, won't give squat for something that doesn't work and can't be easily fixed.
It may also be done for legal reasons.