Is there some inherent instinct to multiply?
Yes
Why do we have kids? And why so many?
To reproduce - pass on your genetics, and so on, so forth. Why else?
There is no possible chance that humanity will go extinct. The population is expanding.
Well then it seems to be working pretty damned well, I'd say.
So what is it that drive us to have children?
The need to ensure YOUR genetics are passed on - if you've survived, odds are, your genetics and other traits are preferable.
It just seems like it's something we're "supposed" to do.
Yep - it's an essential, can't go on without it.
Yes it is.
What else are we going to do to keep the numbers going?
Are people who don't have children somehow deficient?
No - not deficient, just choosing to end their genetic line. Hopefully we don't suffer for it as a species overall.
Is breeding one of our very few instincts?
Yes
We "accidentally" have kids because sex is really really really lots of fun.
Yep - the fun part overrides the dangers and risks.
Which is probably sufficient enough to keep the human population from going extinct.
Let's hope so. If I'm going to suffer for 9 months - and then 9 more - and then god knows how many more troublesome years after that, it better involve a little bit of enjoyment for me.
But most people seem to feel it's their duty as a human to make more humans.
Because it's that, too. Can't it have more than one purpose or satisfying aspect?
It's not "if" we have kids anywhere near as much as "how many" and "when".
Well - these days, in some countries, your odds of having children which SURVIVE to adulthood are much higher than they use to be. So you need to parent less of them. However, in most countries and in our own past, it didn't matter - most of your children were unlikely to enter adulthood.
There is little danger of life NOT going on.
Let's hope so. You never know - some species don't make it purely for reproductive issues. Having high numbers doesn't mean you're exempt from the endangered species list. You never know when the next Bubonic Plague size of a disease will come along - and will be more likely to spread worldwide this time around.