This cannot be explained because there is not enough information out there to support anything! There have been very few studies of naturally wild canines and their daily life activities. The most studies that have been done are with domestic born 'wild dogs' that have only been returned to the wild after being raised by humans. Then humans just want to 'live' with them and 'become like the wolf'!
We can only assume most things about our dogs that make sence to us. We have domesticated almost all canines in the world to where there really are not true wild dogs anymore!! But that is what happens when you put a human in the mix of other creatures, we try to figure them out so much that we end up changing the way they do things naturally.
I am sure that everyone else will pounce on this now that I have said all of this and will tell me that this is not true. My dog does the same thing where he will go out to the garden and pick tomatoes. He LOVES tomatoes!!