system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can anyone have a child but when it comes to adopting you need to be a fit parent?
gpt
Because we can reasonably restrict one but cannot restrict the other.

There is no way to keep people from having kids that doesn't interfere with the rights people have under the law and is also fool proof. Plus, even if there was, you run into the issue of how you are going to determine who is a fit parent anyway? Who sets the standards for that? Are they based on age? Physical health? Wealth? Intelligence? All of those are going to have some draw backs and are not necessarily good indicators of who is a good parent. Someone who is healthy, has enough money and is reasonably smart, might still have the sort of personality where they will neglect, possibly even abuse kids. How are you going to catch that? A simple test doesn't. And how would you deal with people who did not pass the test? Is there a retry option or is one test all you get to determine who gets to be a parent. How do you handle people who get pregnant anyway without a license? Birth control is not foolproof. 

Of course everybody ideally only wants people who will be good to kids to have kids, but we can only implement measures that are realistic, and restricting who can and cannot have a child just isn't.