In modern relationships, men just want to work and come home to a cooked meal and clean house, but their wives are working just as many hours the men are. Having kids means tension in relationship, unpaid labor by the woman, and stress parenting kids. Even if the husband steps up, he still can't breast feed for 3 hours per day.
Pregnancy is really terrible on the woman's body. Post-partem disorders, child birth problems, its just not nice.
Then when you finally get back to your career after 3 months - 5 years, you're passed on promotions, you're n-months behind your peers, and you just don't have the time to hustle for a promotion if you're time is consumed raising kids.
Or if you choose not to have kids, you get financially rewarded for your time. You get more professional responsibility and career development. You get external validation for your hard work (bonuses, promotions, etc). You get full control of your own money, without needing to negotiate spending your partner's money. You get to live in a better location, because smaller places are more affordable near your work. You don't have a 1+ hour commute to your job.
Being a mom just sucks.