This most likely falls in line with keeping up a perceived image of the JW organization.
Yes, there is bible scripture that states that woman should not wear cloths that men wear.
You must remember also that in the US and abroad woman were not wearing pants that much,
not at least until after the Second world war. Some of these dress standards were developed many years ago,
for both men and woman, going far back as the late 50's and 60's. The WTS. tries to shape and mold people into becoming their
sales representatives in front of the public, in this endeavor they've been very controlling and strict upon their devoted followers.
You must admit, if you were to picture a woman out a service with a low cut top and mini skirt, it really present an image of wholesomeness
and virtue. Likewise is a guy came knocking on your door with a scruffy beard, long uncombed hair and a dirty jean jacket, would
pretty much present a similar image.