If you don't buy the concept of spreading the mass laterally to reduce the wing root bending moment consider this ...
Tune in and watch an Olympic gymnast. I bet you could hold your entire body weight by hanging with both hands from one ring directly overhead but I bet you can't do a crucifix. Watch an Olympic champion doing a crucifix and consider the additional structure (muscle) he has in his shoulders to withstand the wing root bending moment!
Works the same way for an aeroplane!
Happy landings!
3 Point