Child free by choice here - never maternal, knew I didn't want children from a very early (mid-teens) age and have never regretted the choice even slightly. Luckily DH was fairly ambivalent, although I think he'd have probably made a great father.
No-one has ever questioned my choice but I do get the feeling sometimes that women who don't have children and who don't have the 'compensation' of being a high flyer in one field or another, are looked down on as being slightly odd.
Why am I happy with my childfree life? Less angst - you only have to read many of the posts on here to see that raising children is stressful, and can be heartbreaking.
I have many instances in my own circle where bringing children into the mix has ruined a marriage - my SIL lost all respect for her DH when their daughter was born as he basically opted out; their DD is heading for university next year and it'll be interesting to see if their marriage survives her absence. Many more instances of separation where kids were a major factor.
I find young children and their 'doings' spectacularly boring. If we had gone down the route of having a family, obviously we would have loved and cared for our own children, but just the thought of having to do the play date, ferrying to endless sport/recreational commitments, all the school stuff etc makes me shudder just thinking about it!
Children don't always (usually 
) turn out how you imagine - they can be difficult, obstructive, argumentative, rebellious - not for any particular reason, just because. Again, threads on here show the angst of having to deal with school refusal, drugs, alcohol, bullying, behavioural problems, illness and disability etc. Evidence of my own friends and family who struggled with children's behaviour at times.
I often think people who are childfree by choice give far more thought to their decision than people who have children, just because it seems like that's what you do.
On a really personal level, I like my own space, and I like peace and quiet. I hate places like theme parks and clattery spaces with a passion.
I also don't buy the argument that people's lives are meaningless without children (mine sure as hell isn't, to me anyway.) Children hopefully grow up and leave home - they may move to the other side of the world, they may decide they hate their parents and drop all contact. Does the life of the parent suddenly become meaningless because they no longer have a child to raise? Were the lives of all the women left single and childless after 1918 meaningless? Has your life been meaningless up until now?
Unless you're going to find a cure for cancer or a way of propelling vehicles with air, I don't think many of us 'achieve' a great deal during our lives. We just live, and if we enjoy the journey, all to the good.
I do stuff that most parents do, I just have the opportunity to do it at my own convenience - I read, listen to music, knit and sew stuff, go to concerts, go walking, go away for weekends, cook involved recipes with DH on a Saturday evening, mooching round the kitchen with a glass of wine and listening to the radio. We have the kind of holidays WE want, so more Loire chateaux, NT gardens and WWI battlefields than theme parks and bucket and spade - our beach holidays are spent in the Hebrides rather than Torquay.
I love our life, it suits us. Children would have detracted, not added.