I am surprised that half the people that have posted here do not want children. I am 26 years old and I really like the idea. I want to have children - ideally three of them - and have a good family. It seems more important to me than other things in life.
I think the last sentence explains your surprise. You value the concept of having a family enough to prioritise it. That will always mean that you will be willing to make the sacrifices required to do so, and in fact, they won't seem like such big sacrifices to you, because the end goal (a family with children) is something you actively desire.
I cannot speak for the others in the thread who don't want children, but for myself, it is not.
I cannot see the joy and delight of it, only the cost, effort and time involved. When it really comes down to it, I do not really care about the next generation, do not feel particularly invested in what the world will be like after I am no longer here, and do not have a burning need to pass on my genetic material nor to create in that next generation upstanding future members of society.
I am content with my comfortable lifestyle. If others want to hear my advice, they can seek it out (and compensate me for the effort!) but I do not feel that my life will be of less import or significance if they do not. It is their loss, not mine. I am of course vain enough to enjoy imparting advice, but it is not so enjoyable that I would want to commit vast emotional and physical resources to that pleasure... which is what good parenting would require.
Mine is a fundamentally selfish position - my happiness is my number one priority - but I do not think that makes it incorrect. It is simply a choice.