Arborists, lovers of wood, craftspeople, and aesthetes have always hankered for more Wood in their vehicles - witness the number of cars and motorcycles which have incorporated a bit of cellulose fiber into the structure or body of their products.
Morgan cars come to mind immediately, as they are yet producing hand-made voiturettes with oak chassis beams to this day, following a very long tradition within the company.
In the 1920's it was not uncommon to incorporate a bit of hardwood into motorcycle frame spars, not for any conceivable necessity, as it would be hard to justify filling a highly-stressed application with a material prone to cracking, rot, attack by critters, mildew, and of course, catching fire, a not uncommon occurence with open carburettor bellmouths, tickled floats, and ignition kickback! 
The reasoning, well, more likely the passion for using wood thus sprang from a deep love for the look and feel of an aged beam, rubbed and polished to bring out the figuration and luster.
It's a passion I share, being a sometime restorer of wooden panelling and bannisters, and I frankly go weak in the knees when I see a tasteful bit of mahogany planking on the deck of a 'Launch' sidecar from the 1930's.
The builder of this wooden Vespa, Carlos Alberto of Portugal, obviously has an abiding love of and skill with the material as well - a few spots of home-layered ply are incorporated for strength, but much of the body is solid boarding, steamed, shaped, carved, sanded, and finessed into shape. Alberto purchased a rotted ca. 1948-53 125cc model, which used a headlamp mounted on the front mudguard, and set about remaking the machine in the materials of his trade.
'Color' has been added by the use of different woods; I would speculate mahogany, oak, and ash as primary ingredients; the effect is very Mod, reminiscent of Paul Smith's signature pinstripes. It's a master -work, and it runs - remarkable.
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