It's not because of "fangirls" per se. It's because American fans are whiney a-holes and anytime anything happens it turns into complaints or *gasp* people sue. People like to "protect" J-rockers in this country and treat them like Gods instead of ... well ... rock musicians. If someone crowd-surfed over here at a J-rock concert there would be livejournal pages devoted to how "disrespectul we are to the bands" as if crowd-surfing at a f'ing rock concert is something abnormal, it'll be morphed into "too many fangirls wanted to grab all over the band" the same old bull argument ... rock stars get touched, rock stars touch their fans. Rockers stage-dive, as do their fans. My God these are ADULT men not children, and the good old "OMG because you all were so horrible the band is never going to come back to America again!!!!" rumor.
American fans of J-rock are a sensitive people. The outcry that would occur at a concert if we behaved as if, well, as if we were at at a ROCK CONCERT would be ridiculous. My goodness, I was crushed so much at the Dir show that my ribs were bruised, but you didn't see me making pages and posts complaining about how horrible the fans were. You didn't see me post negative bull all over forums about how "all of the fans are stupid immature fangirls" non-sense and then dramatically leave the forums by declaring that "you can't stand all of the fangirls on the site". You didn't see me write to JhouseRock and the band's management to tell them that if they don't institute changes you would no longer attend concerts.
However, I did see people ... multiple people ... do just that.
So in short, a concert promoter/manager has to be sensitive to the fact that there are many sensitive puss-babies who grew up in a sue-happy country and don't know a thing about real concerts in the audience, and cater greatly to them for fear of the negative impact it could have on them ... thus, we can't stage dive, crowd surf ... or anything even close to it at J-rock concerts.
Aaaaand on a happier note, I CAN'T WAIT TO SEE MUCC TEAR IT UP AGAIN!! To this day they're still the best concert I've been too ... SOOOO EXCITED.
@BOOBS: If I see you there I'm so gonna ask you to escort me to the bathroom, haha. Maybe I'll even try to stage-dive just to see what happens to me *gets thrown out of the venue*