Because everyone is repressed and has dirty minds and they wouldnt be able to handle the definition that pants bring.
Sure, Hillary Clinton and Angela merkel can do it and nobody thinks anything about it. Bankers, real estate agents, female ceo's do it. Female pastors do it.
Like well trimmed beards, perfectly acceptable in todays society, and even the most upstanding citizens can have them, women in dress pants is still a ways a way for such a backwards religion as the jw's.