This situation usually has nothing to do with having no self respect - actually most the girls who do it are rather confident / arrogant.
Like look at the women on reality shows like bad girls club or jersey shore if you watch them - if not I'll give you the low down.
These women are very beautiful, sexy attractive etc - they can pull any guy they want really. Often they go out and have casual sex with men, just for the sake of sex. Is it slutty? Only because their girls.
The guys of course can go out and have sex with as many girls as they want, and are praised for it.
So for you stressing the point about girls who go out and have casual sex and calling them sluts, your feeding into that double standard and supporting the idea that women aren't allowed to have free sexual choice as men are. Why not?
There's a fine line between being a slut, and having an active / healthy sex life.
Often most people fail to see the difference.
A slut obviously goes around and has sex with several different men, at different times or the same time - doesn't care who the guy is, just wants the sex.
A sexually healthy / active female usually sticks with a boyfriend if she has one, may do a FWB with a very close guy friend (maybe, and only with 1 guy,) or maybe have casual sex with a fling she met on a night out. But that aspect is more rare.
Sexually active / healthy women still have their emotions about them most the time, and would rather have some type of connection with the guy other than sexual. Sluts just want sex, or money / sex, whatever their trying to impulsively gain.
The main thing your describing here however - actually has nothing to do with sluts or sexually healthy women - actually, women and how we express our sexuality is a smaller expression of how society is changing.
We've hit an age where two things are happening; 1 - women are becoming more dominative, and 2 - both genders are fighting for this idea of social equality.
1. Women becoming more dominative.
Over the history of this country, I'd say modern day is the time in which women have the most rights and freedoms than ever. Women have become profoundly more independent, head strong, and ambitious, compared to our submissive ancestors. Naturally, with this new liberated, strong, independent mindset, women are going to do, what the f*** they want to do - regardless of who doesn't agree. Pussy rules the world, so men can complain and other women can complain, but your breath is honestly wasted, as men will continue to date these women regardless.
2. Both genders fighting for they idea of social equality.
Cont in next answer :P ran out of room