Why do people "accidentally" have babies all the time?

i remember back in my parents time when two people had a child it was on purpose and they started a family. but now adays i keep hearing about two people having a child, the man walks out and the woman struggles to support her child. im not saying all the time but look at maury, thats all ya see on that show. now the difference between now and back then is that theres more contraception nowadays. i mean a condom is only a dollar and their found at like a million stores and even in gas stations. and sometiimes parents who have a child by "Accident" dont show the child any love, so the child grows up with bad influences and sometimes the pattern happens all over again. all i gotta say is that if people dont want kids THEN WHY NOT WEAR A CONDOM? it cost only 1 dollar,takes 10 seconds to put on and are found in almost every store and gas station WHATS THE PROBLEM?