I've been on this site for a looong time and one thing that NEVER fails to pop up is that women do not date "nice guys". This is the typical situation I see: the guy who is crazy about one of his close female friends asks her out after being interested in her for a long time and she rejects him. He gets mad and thinks "how dare she not want me, I've been nothing but nice to her" and generally he is right, he has been nothing but nice to her and he would probably make a wonderful boyfriend if given the opportunity. I've been in a similar situation in the past and have had the same thoughts run through my head. However, now that I'm much more experienced I know how wrong this "nice guy" mentality actually is.
The real and obvious reason a girl won't date a nice guy or any other guy she turns down is because she is not interested in him. I know, that's so dumbed down and obvious, but it brings up the next points. What are some possible reasons why a girl is not interested?
1. No physical attraction
Simple, she's not physically attracted to you and no matter how nice you are, it's just not enough for a women to see you in a romantic way if there is no physical attraction. The solution to this is: work out, stay well groomed/clean, and keep up with fashion (that still won't be enough though if you're a "nice guy" as you'll see when I get to my main point). Before you get mad and call women superficial, do you really think you'd date a woman whom you feel zero attraction towards if you have other more attractive options just because she's nice? Yea don't think so and if you say otherwise all you're doing is lying to yourself.
2. Your personalities don't match up
I don't think this needs much of an explanation, she doesn't think you two get along well enough to be a couple.
3. You're too clingy/weird
There is a thing as being too nice. Being too nice can be just plain weird sometimes and seen as obsessive and lacking confidence. Everyone knows the phrase "if it's too good to be true, it probably isn't". It's the same thing with being nice, what are you trying to make up for that you're being that nice? Is that ALL you have to offer? Just being nice? If being nice is what defines you then all you are is a pushover and being a pushover does not scream confidence and women love confidence.
Imagine you're friends with a girl and you casually tell her "ugh I really wanted a snickers bar, but I couldn't find one anywhere around here". An hour later she shows up with a snickers bar and tells you she drove 30 minutes away to get one for you. This is a real life example, a friend of mine did this to a female friend he had a huge crush on and yes he's a very nice guy and no she was definitely not interested in him. Doing something like that is NOT nice or romantic if it's not justified, it's just plain weird. You only think it's going to earn you brownie points because you're interested in her. Imagine if a female friend of yours who you only see as friend did this. You'd think "aww that's sweet, but wtf why did she do this? This chick really needs to calm herself." That girl you got the snickers bar for thinks the same. Big romantic/nice gestures are only seen as romantic/nice if both parties feel the same way about each other, otherwise it shows a huge lack of knowledge of common social rules and social norms.
4. You're a giant pussy
Forward? Yes, but it's simple and gets the point across. This is also my main point. Do you really think a woman is going to suddenly fall in love with you if all you do is be nice to her? Hell no. If it was that easy this site wouldn't exist and most guys would never have a problem finding a girl because most guys are nice guys, it's one of the most common traits. For some reason "nice guys" associate being nice to not making any romantic moves towards women or flirting with them. They believe that being nice is flirting, which it is not, being nice and flirting are completely different. Crazy enough they see guys who actively flirt with women as assholes which makes zero sense (I do have a theory though and it is just a theory). Being nice =/= flirting and flirting =/= you're an asshole.
If you're not properly flirting with the girl you're interested in it only means you lack the confidence to do so and if we know anything it's that women love confidence. This is what women mean by confidence, you flirt with them and show them your interest. The absolute killer combination is to be a nice guy who knows how to properly flirt with women and show his interest towards them. Do you know how weird it is if you go to the female friend you're crushing on and ask her out without ever flirting with her and seeing how she responds? All it means is that you were purposely nice/her friend just so you can win her over, that's not what being a friend or being nice is all about, that's actually very deceitful and an asshole move. The real nice thing to do is express to her that you like her through playful flirting the moment you start liking her in a romantic way.
BONUS. Why women only date "assholes"
It's actually quite simple and you've probably heard it a bunch of times before, the reason women date "assholes" is because they possess traits that are seen as confidence. However, this is not what I want to get across. I want to get across why nice guys view the men women date as assholes even though the overwhemingly large majority are not.
Scenario: Nice guy likes a girl who is dating another guy. The relationship ends and the girl gets sad. Nice guy sees his crush sad and thinks her ex is an asshole for making her sad. What did this "asshole" possess that allowed him to get the girl in the first place? Positive qualities that women search for, most notably the confidence to flirt with women properly. Hence why nice guys view flirting/confidence as something only associated with assholes.
Lastly, what woman would actually choose to date an asshole? No sane woman wants to be treated like shit and/or get cheated on. When a normal woman actually does date a real asshole it's because she was tricked into thinking that the asshole was actually a nice guy (which is clearly an asshole move done by the asshole guy). The only people that do actively search for assholes have issues and you should probably not want to date them in the first place.