I was pretty young in the 80s, but I remember (and have seen films from) that time, and there was graffiti, often very large and garish, almost everywhere. I recall seeing subway trains in New York and Chicago utterly covered with it. While it's still seen, it seems to be much less obvious these days. What gave rise to it in the 1980s, and where has it gone?
Well, in New York City subways at least, the city and the MTA cracked down on it in effective ways. Selling spray paint to minors was forbidden (they still ID you!), and the Transit Authority's security budget was increased. There was more surveillance in the train yards, meaning graffiti artists couldn't get in and do their best work undisturbed. Cars were cleaned rapidly, so that work didn't last long anyway, making it less fun to create it in the first place. And penalties for graffiti got stiffer.
This site has some nice history on the topic.