All jokes aside, men hate wearing condoms.
Cz the pill was getting too expensive.
Coz birth contol fails.
Those answers would be good, if the question was, "Although we dont want kids, even then why we have kids"?
We want to have children cause its part of our natural instinct, to grow the human race by adding into it. The love that we feel for kids is another reason. Sex has very little to do with that instinct or feeling, cause if sex was the reason and a baby is just a logical conclusion then people would never adopt the kids, pleasure of sex alone would be enough for them to live happily.