Bob Moore writes:

In order to reduce the bending moment on the wing spar at the
juncture with the fuselage. Longer airframe life.

But wouldn't putting weight inside the wings cause them to flex
_more_, since the weight is now outside the wing root instead of
within it? That's the part I don't understand.

I guess that if the weight is in the fuselage, and the wings have to
move the fuselage, there might be more stress on the wing roots; is
that what you mean? In that case, I can see where putting the weight
in the wings might reduce the stress at the point where they join the
fuselage; although it still seems that it would put the wings under
more stress when landing, and it would make the aircraft slower to
respond to roll commands (which I presume isn't desirable).

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