I think the reason why people don't realise how prevalent this type of behaviour is, is because women don't talk about it (probably for similar reasons to why they don't report rape).
This thread has reminded me that a fortnight ago, a man on the tube grabbed my arse as I was stepping off. Due to the throng of people around me, my shock and the fact the doors were about to close I didn't say or do anything. I also haven't mentioned it to anyone until now. I suppose I feared that as a average looking middle-aged woman, people like the OP would think I was bragging.
I also haven't mentioned the man who tried to chat me up and followed me around on the tube platform a month or so ago, who I had to change trains to avoid.
Or the man in the shopping centre who said "Sexy Lady" to me, as I walked by with shopping bags in my gym trousers and trainers.
Did I ask for all that? No.
Did it happen, yes.
Has it happen to me regularly since I was a teenager in both lesser and much, much worse forms? Yes.
Do I talk about it? Rarely.
I'm not big busted, I don't dress provocatively, I don't flirt with strangers and if I did it shouldn't make a difference.
I'm a small, average-looking, middle aged woman who regularly gets catcalled and I'm so used to it, I barely notice anymore.
Living in a city doesn't help, but just because it doesn't happen to you, don't assume it doesn't happen.