If you're actually interested in understanding the issue (and not just insinuating that modernity has wrought a monolith of selfish women who keep their affection and childbearing away from men out of spite or self-indulgence), then the new book What Are Children For? by Anastasia Berg and Rachel Wiseman would likely be interesting to you.
https://us.macmillan.com/books/9781250276131/whatarechildrenfor
"Childless Cat Ladies" is one of those terms that is frequently mentioned in common parlance, despite meaning different things to different people. Looking at my own experience and the people I know in my own life, here are a few of the stances or reasons women may have for delaying or forgoing marriage and/or children.
1. Many educated and/or professional women, whether partnered or not, are waiting to get through graduate school and the introductory stages of their careers before having kids. Elite business schools are primarily two years of networking and social events; unless you want to forgo all the dinners out and trips abroad with your B-school classmates, or you have a spouse (usually a wife) who is willing to solo parent while you attend all those outings, it doesn't really make sense to bring kids into the picture at that stage of life. Likewise, medical and law schools (and residencies and clerkships) often require a few moves and undesirable work schedules. It's not that you can't have kids in that time, but if you want to actually see much of your kids during those early years and neither parent is going to stay home full-time, it makes sense to wait. I'm close with a couple in their late twenties/early thirties who just started as attending doctors and want four kids. They've waited to get through residency before trying, and their choices of specialties (peds and family med) were partially influenced by wanting to finish residencies and fellowships on the early side so that they can start parenting with decent work schedules.
2. It's not always easy for women to find male partners. There's a stereotype that women are too picky, looking for 6/6/6, only going after 20% of men, etc. However, I know plenty of women who aren't nearly as shallow as incels and MRA-online types would like to believe, but who are still struggling to find a man. They want a man who listens to them, is an interesting conversationalist, is kind to their friends and family, takes on an equitable share of household tasks, emotionally supports their pursuits, and expects her to be a partner, rather than a second mother. None of those things require height, a six-pack, or a high income, but they're still not that easy to find. Yes, women also want to have kids with a man who provides a sense of stability, but that often just means "has a middle-class job or is on a path to get there" rather than splashy wealth.
Most of the single women I know are settled in decent careers and put effort into building lives they enjoy. This could mean participating in walking clubs, book clubs, fitness classes, D&D groups, etc; they're planning day and weekend trips with friends or, yes, spending time with beloved pets. These women do not typically fit a stereotype of being undesirable in looks and/or social skills. They likely have some sort of regular fitness routine, know how to cook well for themselves, and spend time socializing both with female friends and those friends' male partners. These women are putting effort into creating enjoyable lives, and, while they may actively want to find a male partner, they also aren't going to upturn their enjoyable life to settle for any man. That doesn't mean they're picky in a shallow sense-- it means they would rather stay single than be with a man who they don't like (or, commonly, a man who doesn't even like them, but wants a woman for sex/cooking/cleaning or the societal approval of being partnered).
3. As an earlier poster mentioned, there does seem to be a Russian-roulette element to having children. You can do everything in your power to establish a stable, nurturing, enriching, environment in which to procreate, but that doesn't guarantee that your children won't experience serious challenges (physical, developmental, mental/emotional) that can radically alter your time and finances for longer than just their early childhood years. I don't mean to imply that parents of kids with special needs don't love their kids or shouldn't have had them; I'm just saying that you never know whether you'll have a "typical," well adjusted kid or a kid with severe borderline personality disorder or a congenital condition that means they'll need assistance with feeding/dressing/toileting/etc. for the rest of their life. The ways that those spins of the wheel can alter not just your middle age but your retirement years and finances can be stark. Parents have always had to make those choices, but now that being childfree has become more societally accepted, I think more people are honest about deciding that they aren't comfortable with the risks and uncertainty of being responsible for bringing new people, whatever their needs and challenges may be, into the world.
There are other things I could mention, but this comment is already too long. Really, though, that book may be useful to you if you find yourself frequently considering this topic.