Why Finish Wood?
It may be a chore, but there are good reasons to apply a finish
Finishing experts tell you how to apply a finish but they never explain why you should finish wood. Why not leave a piece in its just-planed state showing the wood’s natural beauty? Is it really necessary to go to all that trouble coating your piece with some combination of oil, resin, or plastic? You bet it is … at least in most cases if you want to protect the piece, preserve its joinery, or enhance its looks.
From Fine Woodworking #215