Why so many kids?

So I know that I'm going to get a lot of hormonal know it all women responding but I have a serious question. Why do you women have so many kids? I get having one or two but why do you keep going? I get that it's your life and if you can afford it then whatever but having too many kids isn't doing society any good. If you have five kids, how many of them are going to do something important? My mom had FOUR and I'm the only one who has a plan for my future and is doing something to improve my life and help others. The rest are my three brothers who want to join the military because (in their words) they don't want to do anything else because they don't want to do college. You can't sit here and say you know for sure all three four five six of your kids are going to go to college. Or have a good job. Or not be criminals. We're over populating for WHAT reason? I am GENUINELY confused. Not trolling. Not trying to get in people's business but I've never seen someone with even three kids not struggle to keep kids in line at the store or walking to the park. 
Side note: The whole "it doesn't affect you so why does it matter" question is ridiculous because it does matter. Over population means more welfare. More school taxes. More unemployment. Everything.  Please come up with a better argument 
Update: I posted anonymously because of the first line of this post. I feel strongly about this because we have so many starving kids who need families and you are popping out kids not even thinking about helping other children who have no one. I also NEVER SAID ANYTHING BAD ABOUT THE MILITARY. But for 75% of the people I know In the military, they tell me it was the easy way out. And they choose the easier jobs. There's nothing wrong with that but that's their words not mine. If I wanted a bunch of nagging close minded women who won't see other people's points I would have made it not anonymous so that you could all harass me  . And America is over populated by people who can't afford their kids. I personally know over 100+ families that have 4 or more children. 10% of those people are still on the same marriage and the same baby daddy. It does affect me when taxes have to go up for paying teachers for over populated schools and more housing areas needing to be used. 
And all of you clearly proved my point of being hormonal and rude as hell.