Jumble, I think one key reason that the woods are finished is the abuse that the bodies take - sweat soaking into the more porous woods and the more frequent use of multiple laminated bodies also has driven that - not to mention that most woods are boring as hell and the canvas is too large not to use.
Now, that being said, if you use a HARD wood (not poplar, considered a hardwood but c'mon) like wenge, cocobolo, bubinga, morado, tigerwood, rosewood and the other hyper dense and heavy woods, it's a sin to go farther than lacquering the body. The reason to minimally finish those wood however is the oxidation that occurs.
if you use General Finishes Arm-a-Seal http://www.woodcraft.com/Product/2007259/9891/Satin-ArmRSeal-Quart.aspx that has a tung oil and urethane base it's as close to naked as you can get once the finish cures. That is the trick with the oil finishes is that you almost need to create an airbox to put the body in to accelerate the drying/curing process that can take a few weeks to complete. Before that it gets tacky and you can booger it up (personal experience). I totally agree that the natural beauty of these darker tropical woods needs to be on display but if you take any of those woods, plane and sand them down and wait a few weeks, you'll notice a dull nap that developed on the surface of the wood. That's the primary reason to minimally finish the wood.
Make sense? If you're down with purpleheart turning dull brown or wenge going gray, there's not a physical reason to finish the tropical wood - it's all aesthetic.