There are many problems.
Problem 1: we have too many people on this planet
Problem 2: because of pensions, a ponzi scheme, we feel the need to pump out more kids, we need to have more kids and more kids and more kids.
Problem 3: Religion. Religion has decided it doesn't like abortions.
Problem 4: people who are unable to bring up kids in their present state, leading to kids who suffer, when we don't need kids to suffer.
Problem 5: It's an emotional issue and logic goes out the window.
Problem 6: Some people believe in the "soul" and think that we are making our own choices and things.