People don't stop to think "oh maybe I should get on birth control" before having sex. Thus a child is born. People don't stop to plan out the birth and well being of their child, they normally just go with the flow. People don't stop to think "hmmm maybe I'm not ready for a kid just yet."
Children are not toys, they are living things and need to be tended to. Watered with love and fed healthy food so that they can grow up to save the world.
When having sex with your boyfriend or girlfriend, you don't stop to think about how it would be smarter to NOT get knocked up! (some people do actually think about this before having sex but, not most people) Sex brings out the animal in us all and animals mate to control the population, humans are one of the few animals that make for the hell of it.
So guys, if you don't want to be a dad yet ... strap it before you tap it and girls ... if your not ready to be a mommy get on the PILL!