Street smarts are something that are invaluable to know, but that you won't know if you haven't grown up in areas that expose you to dangerous or dicey situations. You won't learn street smarts in the halls of a private high school or the sidewalks of an affluent middle class suburb. Instead, you learn them in the run-down, poor, impoverished areas where people keep an eye out for anyone who doesn't belong, just like you do in your neighborhood - only, instead of steering clear of people who don't fit the norm, like you may well, they come over to take a sniff or maybe a little bite.
Each of us has a different level of "protect" and "get" interests in other people. For example, if you see a big, scary-looking man, you probably feel nothing but "protect" instincts - there's nothing you can get from him, but he is a real threat to you... so you protect yourself, and stay away. If you're a single guy walking down the street and you see a beautiful woman, your "get" instincts kick in hard - you probably go want to meet her. Likely, you have some "protect" filter still up - if she looks completely cold or uninterested, you won't approach, because you probably won't get much from her, and you might not be able to protect yourself from rejection and losing face socially.
In less safe places, the people you meet have lower "protect" mechanisms toward you (you're less of a threat than the people they usually encounter) and higher "get" mechanisms (you're an easier mark than the people they usually see)... which means you're a lot more likely to get approached by someone you don't want to meet, for something you don't want to have happen.
Street smarts are really about raising people's "protect" shields and lowering their "get" meters around you, the same as that cold, aloof beauty walking down the street does with men who might otherwise be inclined to approach her - if only she seemed a bit more inviting.