I dress and act very casual and un-flirty, I don't like to meet guys by random approach. I was the same before I had a boyfriend. On a night out when I dress up a bit, still my make-up is minimal, I feel like I look quite innocent and not like I am out to pull. If I get approached I just feel wary because if they are just looking for ANY GIRL TO LIEK ME or sex, then you'd think they would go for the girls who try more to look attractive. But what other reason would you get approached? They don't know you, so it's literally just 'hey you look nice, want to boost my ego by having sex?'. Well, no, not really. I get nothing from that except potentially an STD.
I prefer to meet people through friends, and get to know them a bit before they ask me or I ask them out - because then it at least gives the impression that they like you more than they like a stranger in the street.