For me it's a matter of "once bitten twice shy" - the way I've come to expect a potential threat is from learning by my own experiences and what friends have related that happened to them for the most part. When I was an early teen my cousins and I snuck into a large man-made lake to cool off on a hot summer day; afterward when everyone asked where we'd been we got quite the earful of lecture about drownings and polluted water when nobody could give a reason to stay out simply because it wasn't an official lake.
The only times I was approached in groups like OP mentioned, were all before I was an 'adult' - I frequently pass through 'iffy' areas and the hardest time I've gotten from anyone is a random panhandler at a gas station or a 7-11 - I point to my mode of transport and say "you see I'm on this (moped) already" and they leave me alone. But I get the mooches anywhere I go
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Let's go on out and take a moped ride, and all your friends will thing your brain is fried, but you can't live your life too dirty, 'cause in the the end you're born to go 30