Why's will have you tied up in knots of confusion. There is no real understanding of why someone might do something. Here's an example of the weird shit people do.
Her: Hey! I like you and want to be with you. Lets be together.
Him: Oh wow! Great I like you too, you're exactly the kind of girl I like. In fact I think you're my soulmate. Um....no.
Her: What? I like you, you like me lets do this thing.
Him: The thing is, you are sooo great and so amazing and I feel so inadequate. So no.
Her: So you want to turn a 'could mess up' into a 'definate mess up' over nothing?
Him: No. I like you so much that I must protect you from the shameful and terrible thing which is me. I just know
I'll do something stupid and hurt you so better not to get involved in the first place. You are too good to be with.
Her: You know, you don't have to be so elaborate. This sounds like bullshit just tell me you don't like me and I'll be fine with it and move on.
Him: But I do like you. I adore you in fact. I like you so much that I can't possibly date you. I can't lie and say I don't like you because that would be really inauthentic of me. Instead I need you to realise that you are probably the love of my life and that's why I won't be with you.
Her: No! There must be a way we can work this out. We both want to be together, it's just not fair that you're refusing to be with me over something I can't even understand. There is nothing stopping us.
Him: There is something stopping us, my incessant need to protect you at all costs even from me.
Her: So you're going to break my heart over nothing?
Him: No I'm breaking your heart now, to save you from having your heart broken later by me. And I'm doing this because I'm loving you on a spiritual level that transcends mere mortal lifetimes.
Her: Yeah right. Jerk!
*Walks off*