I dont, however, at all of my nieces/nephews games, everything is UA. All the clothes they wear to school is UA. Go watch a jr high fb game....it's all UA. THe only sport I dont see alot of UA is in bball.
UA is certainly popular, but I'm going to need more than "my niece and nephew wear it" and "it's the only thing I see at their games". My niece and nephew wear plenty of Nike and so do kids on their teams, but I wouldn't say it's more popular because of that.
I'm in youth sports/teams sales and kids still ask for Nike quite a bit. It'll never be viewed as an old person's brand. Heck, Jordan shoes are as popular as ever and nobody under the age of 18 saw him play.