Invictus, how do you know YOUR kids will let you move in with them when you are old, that they will be at your deathbed, and all of that?
Your kids may grow up and not want anything to do with you. They may be broke. Or, with age, you might even end up hating them and who they have become. Most children don't ever truly get along with their parents.
I'm with Putin33 on this one; if we lived in any kind of remotely human society that provided a universal living wage to people, a society in which people did not have to make decisions about whether they should have children based on some kind of hedge with the future for insurance of material interests, or insurance of love out of fear of abandonment once they reach old age and are not economically useful to the establishment because we live in a Dickensian world of grotesque inequality and injustice (that would be "a bad way to go", as Invictus puts it).
I think the dog-eat-dog nature of our world and lack of real safety net actually connects directly to the very reason people may want to have kids for that insurance, but it also connects directly to the reason why your kids may grow up and not want anything to do with you. Most kids stay with their parents because they wouldn't have access to a bed and a meal unless it is at home with your biological parents or possibly legal guardian. But our gene pool is has so much variation, and the world of information is so saturated in the 21st century, that your kids may grow up to have such a radically different mindset from you that, if they had a different means of living growing up, they would go live elsewhere. (Maybe if kids could be allowed to pick different parents at a certain age, maybe a huge portion of them would opt for different parents?) I wonder what the statistics are on people who simply do not get along with their parents? Plenty of kids move away from their parents as soon as they possibly can, and would do it even earlier if they could.
The whole taking care of people in old age, it's this burden that society puts on us because we refuse to take proper care of people as a society. So when old grandpa is dying, instead of providing him with some dignity and a reasonable subsistence, we, as a society, make his family (who may not even like him) bear the entire burden.
Anyway, I believe most people are not actually consciously aware of the majority of the real reasons and influences behind their decision to have children, and a lot of those reasons would be denied even if they did arise to consciousness (peer pressure, for example).
And finally, Invictus, when you imply that people who don't have children will not have anyone to be there for them in old age, that they will probably lead a miserable existence in the end, is kind of offensive. Maybe it's something you need to say to yourself because you secretly resent all the work you put in to raising your kids and you need to believe that all the "free fun" we are having, as you put it, will ultimately be punished by a miserable death, but please don't share that view with others; just say it to yourself if you need to.