I'd say you're absolutely correct. I laugh when I see feminist friends of mine who complain about "creepy" guys approaching them at coffee shops and days later they'll talk about how they hate being single and want to meet someone.
I guess this is just how the human mating game goes. We try to make some things make sense intellectually even though there's probably deeper subconscious and chemical messaging going on.
Everyone has a bunch of biases they're more or (mostly) less aware of, thus https://en.wikipedia.org/wiki/Predictably_Irrational
My point is though: By putting yourself in a public setting, you are more likely to be approached. I don't want to say "asking to be approached", but I'm not sure how else to articulate my thought |:)
I wouldn't be shocked if a stranger approached me in a coffee-shop. I would be if they approached me in my home!
I'm not shocked if a stranger approaches me; I consider them unable to recognize the social situation and they are being rude. I also grew up in the city, where the socially polite thing to do in most public situations is to leave people alone.
I go to coffee shops because I like the laid back atmosphere of many of them. I also like the smell of coffee and people watching.