digging maples

I noticed again, today, something I've often seen.  When trees grow on ledge the roots go out instead of down, making them easier to dig and move.  However, any tree over 6 or 8 inches in diameter can hardly be considered easy to dig and move.  Sugar maples dig quite well in the fall- the ground is moist and there are no leaves to suck water out of the tree-  alos there are lots of them every where.  I would think more people would dig them up from the woods rather than buying them from a nursery.