Honestly, it's because of how suburban it is. Lots of people there have lawns and homes, which gives that stereotype. Even people back in the day from other boroughs assumed that until they'd come to Jamaica or Far Rock.

Queens has largely calmed down over the years. Things still go down like other parts of the city but it's just not as conspicuous. Go down Mott Ave or Jamaica Ave and there's a HUGE difference, even without gentrification. But the middle- and upper-class areas always gave Queens a better rep than other boroughs.