Our standards of dress are not set by worldly people. We are the ones who SET our standard. However, we do consider what is generally acceptable to the world in respect of our role as ministers, because we want to follow the example of Paul and "become all things to people of all sorts" (1Cor.9:22), whilst at the same time not "giving any cause for stumbling" (2Cor.6:3).
Because the GB has prayerfully made this consideration, that is why brothers now are, without criticism, able to wear a neatly-trimmed beard if they wish. They may also dispense with jackets and ties in general, apart from meeting program assignments. Sisters can now wear slacks, also apart from meeting program assignments. An over-riding principle is that the garb we choose to wear, whatever the situation, does not appear "casual".
In setting these standards, the GB will have given some consideration to how the world in general views the appearance of those claiming to be "ministers", but with far more weight given to honouring Jehovah, especially when carrying out duties relating to the ministry.
A great deal of discussion has been generated over local elders making rules over and above the direction provided by the Governing Body, particularly regarding the dress code for support duties in theocratic meeting situations and in certain field ministry situations. Requirements set by local elders appear to differ.
The absence of specific direction in certain matters indicates to me that the GB wants to allow us freedom to exercise our consciences and good sense in respect of how we appear when carrying out a range of ministerial activities. It seems there is also an extra space for the exercise of "reasonableness" on the part of those who have a delegated responsibility to keep things "orderly" in the congregation. For example, an insistance on brothers wearing jackets and even ties in activities in or outside of theocratic establishments where the ambient temperature is uncomfortably high and a cause of excessive perspiration is, (to me), unreasonable, and actually achieves the opposite of what is intended. (Reminds me of the collapsing British guardsman parading in full uniform in the summer sun!).
The principles illustrated by the experience below is enlightening, not least because of when it was recorded.
*** w88 9/15 p. 30 Christians—Firm yet Flexible ***
The elders may feel that generally a certain form of attire—such as a jacket and tie for men—is appropriate for door-to-door preaching. Such was the case in a congregation in a South American land. Nevertheless, an elder there learned that a young man was holding back from sharing the good news with others. The reason? He could not afford to buy a jacket and a tie. The elder concluded that flexibility was in order and therefore encouraged the young man to begin sharing his faith with others.
Perhaps a little research on the practice of infantilisation is needed? Are we really in the position of those described at 1Cor.1-2? The GB appears to think not. And our willingness to apply what is said at Heb.13:17 gives weight to that.