People have sex for pleasure. That's a fact. Sex is not automatic consent for a pregnancy, especially if a contraceptive is used. That's why this recent hobby lobby decision is so hilarious. Because contraceptive use reduces the need for actual abortions. But apparently abortion in the eyes of the religiously zealous is now defined as "preventing an egg from being fertilized".
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This idea that sex is only for reproduction went out of date sometime in the early 20th century. I'd say it's starting to stink from being rotten, but at this point it's really just sun bleached bones.
Considering the amount of lamb-bladder condoms and recipes for contraceptives and abortion potions we've found in ancient texts, sex being only for reproduction was actually a rather cult-only idea.