I think the JW dress code is a product of Brooklyn Heights and lower Manhattan. The GB, writing staff and Bethel family see bankers in lower Manhattan going to work in a full suit (probably the only people in the world that still work in suits- except for lawyers when they're in court). So they think that suits are what respectable people wear to work.
Beards are for hippies and college students (GB is terrified of the village, soho, NYU any area where there are free-thinking hippy homo types- their words, not mine)
If Bethel was in Montana, or Florida, or South America or anywhere else, I have a feeling that the dress code would be different.
Side note- Have you ever noticed that the pics in the magazines seem to never show a woman wearing pants (and especially never wearing jeans) You will see women working in gardens, cleaning houses, etc but wearing a dress..
What a victorian bunch.