The typical failure rate of the "pull out" method is 19.% Hope you folks have fun paying child support.
The failure rate for couples that use this method correctly is 4%, but that's way too high a risk if you're really not okay with getting pregnant. Not only that, the general age group that frequents NG has no idea how to control their orgasms, so they wouldn't be able to use it correctly anyways. That, and the whole thing with pre-cum that's already been mentioned.
During the baby boom of the '40s and '50s, the pull out method was the main method of birth control. You see how well that worked...