Since joining OKC, I have spent some time thinking about why people have sex and which of those motivations makes sense to me. I divided up the reasons into good, bad, and problematic, but those categories are just my opinion. Feel free to disagree in the comments!
-Desire: Two (or more!) horny people find each other and fuck. Tale as old as time.
-Procreation: Sometimes people want to pass on their DNA, so sexy times become all about making babies. Often this kind of sex goes along with ovulation calendars and the ingestion of prenatal vitamins. For some reason it is socially acceptable to tell people that you're "trying to have a baby," which means your friends and family now have to picture you and your partner boning without birth control.
-Love: In a relationship, sex can be more about connecting with the other person and fostering intimacy than satisfying carnal desire. (Not that the two are mutually exclusive.) Also, if you love someone, then you might choose to have sex even if you aren't horny because you like making the other person feel good. (Note: I am not saying that people in relationships owe each other sex on demand or anything coercive like that.)
-Boredom: When nothing looks good on Netflix and you're all caught up on GT, what better way to pass the time? For some people, sex is recreational and can help break up the tedium. Who doesn't feel better after a nice orgasm?
-Control: Duh. Using sex to manipulate or hold power over someone else has to be among the shittiest things that one human being can do to another.
-Obligation: On certain occasions (Valentine's Day, anniversaries, birthdays) people feel like they MUST HAVE THE SEX because society tells them they should. If you enjoy going out to a four course dinner and then getting it on to commemorate a third-century Roman martyr, then go for it. But I don't like the idea that someone HAS to have sex. The same applies to people who fell like they MUST have sex by the third date or fifth date or whatever. Have sex when you want to have sex. Period. Or even on your period, though some people find that gross.
-Exercise: I have heard people claim that "sex is their cardio," which is dumb. You don't actually burn that many calories during intercourse. The average for men is 100 calories and for women 67. If you don't want to work out, that's fine, but don't try to equate sex with a spin class because that is nonsense.
Problematic Reasons (ETA: By problematic, I mean could be good or bad):
-Money: I support sex workers who chose their profession of their own free wills. However, all too often the sex industry exploits the vulnerable and goes along with human trafficking. If prostitution were legal, then maybe the sex workers could keep their profits instead of giving money to pimps or other abusers.
-Validation: Sex can be empowering for sure, but I don't think it is healthy to use sex to prove your own attractiveness. Looking outside yourself for validation means that you base your self-worth on how others see you, rather than valuing yourself regardless of outside opinions.
OK, so what reasons did I forget?