To be honest, lacrosse was popular here well before it became a trend a decade or so ago. I am in the affluent part of my city and every kid goes to private schools so I think it an aspect of that subculture. The girls play field hockey, it's really popular but my middle-class public school self had never even heard of it until we moved here.
I like flag football a lot. There are adult leagues too, coed and men’s only. The NFL is smart to push it; kids that excel can eventually transition to the real thing while the rest enjoy it and learn the finer details of the game and likely become bigger fans of NFL teams.