That's not always the case since contraceptives are not 100% effective. Some people try everything not to get pregnant and then as much as they have tried to prevent the issue - it's happened.Accident may be prevented with proper planning, and thinking. Accidents come to people who lacks thinking. No offense to anyone, Its my opinion regarding the matter.
But sadly quite a few people these days just don't bother with contraception at all, and then are suprised when they get pregnant. blue_shocked