Perhaps the heli pilot hasn't been affected because he has been separated by ATC?
More likely because of our steep climbout we avoid any wake turbulance. I've departed many times within a minute of 737s and such like without any problems. As I said, I have felt it behind another helicopter(and from my own at times when orbiting), but it's just like driving over a bumpy road. I admit it could be different in an R22 or suchlike.