I think there may be a few extraneous variables in that study showing the relationship between diabetes and rubber soled shoes?!?! Obesity. Lack of exercise. The sale of those shoes is just coincidental compared to these major ills facing our society, and increasing the rate of diagnosed diabtetes.
Also, my feelings about playing barefoot are not swayed by a cultural norm, rather a true feeling of disgust when I see a male playing music with pasty, white feet. If anything, it is the "jam band" culture that prompts you to play with no shoes on.
All's well that sounds well.