"the big question is why still so few women in aviation."
Is it the big question? I thought it was fairly obvious - the majority of women simply aren't interested. There's no disputing that on the whole, certain genders tend more toward the skills needed for certain careers, and while I'm sure its a lot less of a 'thing' than it was even 30 years ago when I was a kiddie, there's still an element of social conformity to roles. 8 year old me liked planes, people would suggest I become a flight attendant, not a pilot.
Hit one of those 'is your brain male or female' tests and I bet all the women pilots and engineers are veering into the 'male' category. I did one a while back and found myself 25% into 'male' while the average for women is 50% into 'female'. So I'm rubbish at having an emotional conversation but pretty handy at reverse parking.
I would hate to see the aviation world striving for 50:50 representation of the sexes - if you're interested, do it. If you're not, don't bother. There's nothing worse than forced equality. If you need it handed to you on a plate, through special recruitment schemes or targeted advertising, you didn't want it badly enough in the first place.
Likewise women in politics, the fire service, men in midwifery....