For my thesis, I had to buy 9 8-feet long 2-in diameter shagbark hickory dowels and it cost (my grant) 300 bucks for that wood. I called approx 200 lumber yeards and wholesale distributors and found that anything over two inches isnt produced due to problems with checking (splitting in the drying process).
That is some of the nicest wood i have seen. Just beautiful. You can, however, get Maple and such at larger sizes.
What we do know is that Hickory is used commonly as tool handles- as you mentioned- for the reason of hickory's ability to withstand shock loads so well. For that same reason it is used for baseball bats. I was able to locate alot of sources of hickory, as it is a common wood being turned out in many lumberyards in the east coast and north mid west, but none made seasoned cuts above 2 inches in width due to checking. I could get it "green" (unseasoned) pretty easily at larger sizes, though.
What nags at me is that hickory has a very high modulus of elasticity compared to most North American woods. In plain english the MOE is how wood bends. A higher number means more resistance to bending. It also has a high modulus of rupture. This means an ability to not break whilst bending. For instance a wood used for bows (i.e. bows and arrows) would want a low MOE and a high MOR. it seems you want a neck to be both stiff and sturdy, or to be high in both of these values.
White ash (the strongest ash in these properties)
MOE - 1.74^6 psi
MOR - 15,000 psi
Rock maple
MOE - 1.83x10^6 psi
MOR - 15,800 psi
Shagbark Hickory
MOE - 2.16x10^6 psi
MOR - 20,200 psi
Hickory looks just beautiful too, takes shock loads extremely well, is very hard (tough to dent), and can be had commercially in widths of 2 inches.
Im confused why hickory isnt used as a bass neck when it is used for baseball bats. Hasnt anyone thought of replacing a p-bass neck with its analog?
Theres much stronger commercially available woods out there too.
Compare with Greenheart - a wood used in the construction of instruments
MOE - 3.25x^6 psi
MOR - 24,900 psi
We also import south american woods, such as Ipe, for decking and African woods, such as Azobe for railway ties.
Ipe
MOE - 3.14x10^6 psi
MOR - 25,400 psi
Azobe
MOE - 2.47x10^6 psi
MOR - 24,500
Link to info
There has to be another reason rather than mechanical properties. Is it tradition? It seems to me that one of the biggest problems with bass necks are the ability to control the forces generated by the bass strings. We have double truss rods and such to control these loads, and yet still there are problems where necks are destroyed. Rupture creep (read fatigue) is another problem exhibited by wood. Most of these problems can be alleviated by using a wood with higher values of MOE and MOR as listed above. Im not certain why these woods are not used.