People screw up, all the time.
But yes, sometimes people have kids, realizing that they have no clue how they'll afford them. Call it desperation, if you will. Or rebellion against an unjust society.
Or maybe they don't really think it through. Much of the time, I suspect.
Really? In 2018, given the myriad of ways you can cost-effectively prevent pregnancy, I hardly accept "because it happened" as an answer.
Yes, birth control sometimes fails. That statistic alone cannot explain the quantity of individuals having children, who simply shouldn't be. People can down vote me all they want, but what I am saying is true: Having children when you cannot afford to take care of them is reckless and incredibly selfish.