I think neither sex has yet come to terms with how fast the world has changed.
A hundred years ago, the vast majority of men would have gone out to work in the factory and the vast majority of women would have looked after the house and raised the kids. Neither party had many aspirations above this because the world wasnt like that, opportunities, perhaps more accurately - temptations - werent available. Men were happy down the local for a couple of pints after work on a Friday and housewives socialised with other housewives.
Compare to now. There are a myriad of hobbies we can all choose from which are way more exciting and self fulfilling than going home and looking after kids or doing the chores. The vast majority of us have enough money to take advantage of these temptations, whether its gadgets, tv, sports, gym, holidays or whatever. Personally I mountain bike, which requires me taking a day or sometimes a whole weekend away driving to and riding at the trails. How can kids and family life fit into that, they cant.
But underneath this layer of temptation there is the desire to have kids, and to pair up with the opposite sex so as not to be alone. These are basic human needs. Raising kids should be satisfying, it was enough for people in my grandparents generation.
Some, perhaps many, people are able to sacrifice these temptations for their family at least partially. I did, for many years when I had my young kids at weekends. But I wasnt fully satisfied with life because the temptations have a pull on us all. The grass always looks greener on the other side of the fence. This causes resentment, stress, dissatisfaction and potentially depression. One hundred years ago these temptations simply didnt exist. This has the effect of making raising kids not seem satisfying any more, as its seen as giving up the 'freedom' to partake of these temptations at will.
So what happens now? The men and women who have less ambition, fewer aspirations, still have kids because its easy and simple thingto do. So do the ones who somehow are able to genuinely get satisfaction from a family life and make it as fullfilling as they can. However there are a group of men who desire more, probably above their natural station, who ideally would live a bachelor lifestyle if it wasnt for the natural desire not to be alone. When they find a partner it is likely that she wants kids (most women simply aspire to that one thing), and the man feels unsatisfied and trapped.
High flying women, who've postponed having kids are then trying to get men who are probably at a point in their life where they can now afford to try out some new activities and get some excitement in their life, and care a bit less about needing a partner especially if they are finding other ways to occupy their time (i.e not lonely or bored).