'The Warriors' trailer makes very little sense

To celebrate my entering the 21st century by subscribing to Netflix, here's the trailer from the first movie on my queue: The Warriors. What? It's a classic, shut up. Anyway, what's interesting about the trailer is that two of the first three gangs pictured (the Boppers and the Hi-Hats) aren't even in the movie beyond the first scene, and the Rogues, who are the cornerstone of the plot, aren't mentioned at all. Still, it's a fun glimpse into a fantasy world where the streets of New York were divided among a series of flashy, color-coordinated gangs.