I don't know if it's the same for everyone else but growing up I was told you're supposed to chase girls and that if you don't actively pursue them you'll end up alone. I think that's where this kind of thing comes from.
Obviously if she says no and leans away, you stop and don't try it.
I'm pretty picky about consent. There are men who know how to delicately signal their interest and invite me to signal back whether or not I am amenable. I have the general impression that such tactics get men a lot more action than tactics that intentionally step on a woman's boundaries as a matter of course.
But there are also many women, in my experience, that for whatever reason, don't or can't signal their interest or intentions. In that case I ASK them. It sounds very awkward to say it, but if done in private (i.e. you don't shout it out) I've actually noticed it creates a lot of comfort in the women. e.g. once I asked a girl I was on a date with, and she said she wasn't comfortable with PDA (we were inside a bar). I didn't push it, but after we left the bar and nobody was in sight outside, we did make out. I like to think if I had just "gone for it" in the bar, she would have been uncomfortable, I would feel rejected, and generally bad things all around...
But I still hear LOTS of people say this and it's exactly what I'm talking about. Everyone keeps saying men need to be aggressive and I really do think that's what causes a lot of the sexual harassment.