Sexual Relationships 
Sexual Health 
Whether you like it or not, body count does matter to a lot of guys, and women always wonder why, and I think it's one of those thing that only a man can understand, but I hope my take will shed some more light on it so more women can understand. I'm also going to keep it relatively short and simple because who wants to read all day.
1. Religion
I'm just going to knock off the most obvious reason first. It may be a very small portion of men but it's still a valid reason.
2. Sexual Value
A lot of men have more value in their sex life and wants a woman who did the same. Some men are only willing to have sex with someone they're willing to spend the rest of their life with, and they don't want to be with a woman who slept with men on the same night she met him.
3. Self value
The value you place on yourself greatly matters in a relationship. A big reason why people who are fat, out of shape, dumb, lazy and have poor hygiene can't find partners is because of how little value they have with themselves. If they don't value themselves enough to take care of themselves, why should anyone value them in a relationship. But for a lot of men this includes sexual value. For these men a woman who places her sexuality to a higher standers and sleeps with less or no man is much more valuable than a woman who gives her sexuality to any man who turns her on in the moment.
4. Likely relationship outcomes
There are studies that show that couples who delay sex have happier and healthier relationships. People who had a promiscuous past are more likely to cheat, they're not always bound to cheat, but they're more likely to. Also promiscuous people are known to think that relationships are just disposable and replaceable since that's how they treated their sex life. Recently my mother found some of the women she went ti high school a college with and almost all the know sluts grew up to be fat and gross, they have a filing cabinet worth of divorce papers and are single mothers raising multiple kids from multiple men and living off tax funded welfare.
5. Promiscuity is just gross
We live in the age of hookup culture where haves lots of sex with lots of different people is almost the norm. Some like it and there's nothing wrong with that, but some people (men and women) think it's disgusting. Some think it's a cesspool and an abomination, including me. There's nothing morally wrong with it, but some people just doesn't want anything to do with it. Also lot of guys don't want to put their mouth on a snatch that a lot of other guys nutted inside of.
6. Insecurity
We all have insecurities, I have insecurities, you have insecurities, Dwayne Johnson has insecurities, and that's normal, and men caring about a woman's sexual past has a lot to do with insecurities, I know because I'm one of them. Some men aren't confident in their sexual performance and want to be with a woman who can't compare, some men are insecure about their own sexual past and some men are like me who is a virgin and would only date other virgins because we don't feel comfortable being with someone who was fondled by another man, and you know what, it's okay to have these insecurities, what matters it that you find someone who you feel truly happy with.
Bonus: Men who slept with many women are not champions
I always see women try to make the argument that men think male sluts are "Champs" and female sluts are "Tramps", and this if not the case at all. Men dislike male sluts as much as that dislike female sluts, and they are not champs at all. People tend to think they're champs because movies and TV shows paint the picture that the guy who pick up women at the bar is the "cool guy", but if you step out of entertainment and into reality, the only people who think they're champs is them egotistical selves and their equally douchy and equally egotistical friends. In a mind of most real men, a man who can stay loyal with one woman and raise a great family with her and be a excellent father to his children is infinitely more of a champion than a man who fucked a million easy club skanks. That's because being a devoted husband and father takes loyalty, commitment, patience, skill, drive, courage, intelligence, flexibility and strength and it seems like too many lame ass boys bitch out when things get tough on inconvenient. Hooking up with 100 Tinder sluts is something anyone can do.
What Girls & Guys Said
0 2I'll add another one for you. To ensure paternity. We wanna ensure that we are the father of that kid, and a promiscuous woman cannot ensure that for you. It's devastating and debilitating when a man finds out that the kid he spent years providing, protecting and loving was never his when he thought that it was.
Good list, especially #4