All that wood that you mentioned has been sealed with paint or some other finish. Have you never seen what happens to the wood on an unfinished fence, porch or barn? Cracks/splits/warping galore...
Is your fence made of rosewood?
Do you expose your fretboard to:
Sun, acid rain, snow, wide humidity swings, huge temperature swings?
The framework supporting your home doesn't get sealed,will last for 100s of years. The undersides of floorboards don't get finished.
If you are going to make an analogy make a valid one.
The undersides, and insides of furniture is NOT finished or sealed.
Ever see antiques roadshow? Seems like there is plenty of raw woodworks that are several hundred(s) of years old, and have held up well.
The majority of the moisture is lost from endgrain (the vascular system of the plant.) Sealing the endgrain is a preventative method that is far more effective over time than an oil film on the surface.
Oil is not "moisture"
Oil softens and weakens the fibers.
"Lemon oil" is mineral oil with acids and solvents.
Oiled wood holds dirt/dust.
Oil as a sealer, as a cosmetic facelift is fine just don't buy into the marketing hype.