There are lots of reasons for the gender pay gap. Most of it isn't about men being paid more than women for doing the same job (although just because that's against the law (and has been for 40 years) doesn't mean it's not still happening).
There are lots of reasons for the GPG including traditional male & female roles. It's also about how we progress during our careers - there is still a glass ceiling in many sectors even before you factor in having children and the impact that has on women's careers.
IME a lot of very able and talented women are passed over for promotion and progression (or take themselves out of the race) because of factors such as long hours culture, having to work away more, having to be able to go somewhere at the drop of a hat.
The stupid thing is, women have a lot to offer in all sectors and many businesses and other organisations are much worse off as a result,
This was recognised when the targets were set for getting women on boards of big companies.
It's in everybody's interests to keep more women in the workplace and to do that roles and arrangements have to change otherwise working women just cannot do it.
Once upon a time women couldn't work in factories because for one thing there were no toilets. Things had to change. I was asked about that very issue in my first job (employment lawyer). The woman had to use the office toilets. I have also been asked many times how to sack a pregnant woman (first time was in 1997, last time was this year but that's another story...)
It's fine to say more men need to take care of the dc's but for many that's not an option. It's making it workable to have dc's and a career that will make the difference.
The crazy thing is, a working mum with a job that works for them is one of the most reliable employees an employer can have. Employers just need to wise up to that and make the most of it.
And when push comes to shove, remember most of employing people (for a large part of this country at least) is doing what you can get away with.