The answer is that there are still a lot of people who hold on to the idea that the 'role' of a woman in society is to have children, and whether conscious or not that is what is coming out in these conversations. I don't necessarily buy into the 'misery loves company' argument. Frankly that sort of argument makes the same mistake as the people you're complaining about; it assumes that people who have kids must be miserable because they're doing something that you don't find appealing. Which is, of course, quite wrong. I have no doubt that there are some people who regret having children for a whole host of reasons, just as there will be those who choose not to have kids and go on to regret it. But as much as having kids has all of the downsides you mentioned, and indeed many that you're not aware of, for a lot of people who have kids the positives more than outweigh the negatives. In practice people who judge you for not wanting to have kids aren't doing out of some sort of envy, but because society as a whole is still struggling in large part to accept the idea that a woman may genuinely not want to have kids. And there is a patriarchal element to this, because it is women that get judged for it far more than men do. Unfortunately whilst it is hopefully something that will improve over time, it's still an issue and not something for which there is an easy fix.
The irony here, of course, is that you're 22. It's entirely normal not to be attracted to the idea of having kids at that age. You're practically still a child yourself. And you're right that your mind may change in future. But if it doesn't, that's fine too. Even though I have children I am amazed at how society still normalises the idea of women going through labour and childbirth, because it is incredibly difficult and traumatic both physically and mentally. I wouldn't judge any woman for not wanting to go through that. Same applies to the other challenging aspects of parenting. For me the positives do outweigh the negatives, but if you don't want those negatives and want your life to take a different trajectory, that is absolutely your choice. At the age of 22 I'd say having that mindset is positively normal. As much as I hate to say it, for women who are in their 30s and 40s and don't have kids, that scrutiny is often worse because they won't change their mind at that age. As I say, I very much hope society's attitudes have become more progressive by the time you are that age. Either way, the most important thing is that you make the right decisions for you. If others judge you for that, then so be it. If it's in passing, brush it off. If it's friends or others you see more regularly, spend time with those who do support you and the choices you make.