Clothing Answers

Why do Jehovah's Witness dont were pants during church?

You are no doubt referring to the women, since men do wear pants at our meetings.
Jehovah's Witnesses believe that God's holy spirit is present at our meetings so we strive to dress in a manner that shows reverence for God. So, Jehovah's Witnesses dress for meetings in the most dignified manner possible according to the cuture of the area that they live in. In western societies, that generally means that men wear suits and women wear dresses or skirts.
That does not mean that there is never a time when a woman may be wearing pants or a pantsuit to a meeting. There may be an interested person that might come in for a meeting dressed differently. JW's will always welcome such a person, never judging them based on appearance. Also there may be occasions that a Jehovah's Witness's work schedule dictates that in order that they be at the meeting, they have to come in work clothes. That situation happens rather frequently. In such cases, that person is not looked down apon. We are just glad that they could be there at the meeting, and often other members of the congregation will make special effort to speak to that person, telling them how glad they are that they could be there.

Based on my experience I would say it is purely traditional. There is nothing as far as I can see to say that sisters cannot wear trousers to meetings but it is simply not done.
The last time I actually saw a sister wear trousers purely as a choice was in about 1980. It was obviously something that struck the congregation as odd for no reason other than it was 'odd'.
I know most sisters in my neck of the woods that wear trousers to work who will go home and change into a skirt and would rather be late for the meeting than turn up in trousers.

As to the reason why, as I said it is simply one of our friendly little unwritten traditions such as brothers not being used at conventions if they have a beard. No harm is caused.
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