Why women can't do microphones
The organisation ties manliness to assignments. That's why you have arrogant window washers who drive cars from 1985, because they so high up in the organisation, no matter how much they suffering financially, they think they are God's gift to men, because they give talks at assemblies or are part of the AV team or whatever.
A lot of men struggle to do tasks that are mainly assigned to women, cooking, cleaning, childcare, etc (Although i find them theraputic). This is why it's so difficult to get brothers to volunteer for cleaning assignments. They waiting for other tasks they consider manly, where they can be seen and praised. Allowing women to do these tasks lowers their value in the eyes of many men.
How do you create an elder? You start him on microphones as a young man. These assignments handled by men give a young man a sense of self worth. This encourages him to grow in the congregation. Microphones > Platform > Sound > Attendant > MS > Elder > CO etc etc.
By allowing women to do these assignments, they cheapen their value in the eyes of many brothers who will lose interest in doing the assignments, affecting their growth within the organisation.
Sisters also make up the majority of congregants, so young brothers will have to wait months to do microphones, further killing his spirit.
Another issue is that many elders are old and worked hard to be where they are and aren't willing to hand over positions to brothers who haven't proved their worth, regardless if whether the GB says a 20 year old can be an elder, the older elders are not having it.
Doing microphones or literature or any assignment faithfully, week in week out for like 10 years usually gives elders the confidence to move you up. It would be hard for old school brothers to assign a brother as an MS if he sits for 90% of the meetings because sisters are doing the microphones.
This is why they'd rather use unbaptised brothers, because it will keep them in the system and encourage them to grow within the organization.
I used to read the Bible study paragraphs when I was an ubbaptized 10 year old because there was only sisters, no other brothers. Once we arrived late and found sisters reading, and they were 100 times better than me. The conductor immediately asked the sister to stop reading so that I could read the remaining paragraphs, even though I made 20 reading mistakes per paragraph.
So sorry, it will never change. The survival of the organization is dependant on males valuing these assignments