I agree. The fact that a "bike rack with strings" could have as good of a tone as many solid body guitars, because very little resonance actually affects the pick-ups/makes its way to the amp, especially with the help of today's technologies. Its a bit of a myth with many guitar that "the feel", especially of the body, can only come from trees.

We're all tree huggers. We rely on them for shelter, paper and many other things. On the other hand, a farmer can plant and grow a square mile of hemp, which can be used as a replacement for trees in countless ways, not to mention that it is very hardy. This doesn't relate exactly to guitars, but it is a hint that the industry exists as it does because if a mass change of product reliance took place, many people (in the forestry industry in this case) would be out of a job.

There are companies experimenting with other materials, some of them making lovely guitars...