I just visited Jasper, Alberta, Canada. Many of the flower and shrub beds had small, intact pine cones as ground cover in and between the plants. It was unique and enchanting.

There is no real good reason why you could not use them, just as any other type of organic matter could be used for mulch. Left as they fall off the trees the cones would leave too much space, for light to reach the soil, to be effective as a "weed" control unless something else was added, but I have noticed that where pine cones are relatively thick slugs are less of a problem.

I rake my own pine straw and when I am lazy I leave in the pine cones. They can look nice in the beds and break down all the same. You could crush or chip them with a nice mulch being the end result.

I toss them into the pathways between my raised beds. Just walking on them breaks them up, so I don't bother to shred them.

I used to shred them in my chipper-shredder until my shredder died (too many pine cones?). Made a very nice mulch. Stuck like velcro to my dogs, though.

tj