I would explain it as follows (why people like to have recreational sex, not just men): there are more people to whom you are sexually attracted than would make a good relationship. Having sex is about fulfilling lust in response to a pretty primitive biological attraction. Love is something else entirely.
I find your responses very old-fashioned and modeled on the idea that for women, sex is something to be given away, grim, gives you a bad reputation. This is very out-dated thinking. Why on earth can't a woman enjoy sex with a sexy good-looking man? Why do they have to have a relationship with them- I have met lots and lots of very good-looking men in my life but very few that had the combination of possessing an amazing intellect, being emotionally mature, available, successful and caring and all the stuff I was looking for in a man.
Some people do equate love and lust, I have a friend who does and internet dating for her was a misery for the reasons Dahlen specifies- people are not upfront about what they want and so she got hurt many times.
For others though, lust and love are two entirely different beasts.
You can say it is grim or will harm your reputation if you are sleeping with multiple partners, but to whom? Who cares? Their behaviour is obviously fascinating to you in some way.