Same reason Beckham takes all of England's. Because he once took a good one and everyone "remembers" that one and confuses it for consistency.
Well he's the only player we have that I can recall scoring one since Werling's about a year ago. He hit the target with a nice one early on. The problem we have is that we don't ever score by crossing them, so Howard/Leon etc just think "Well we might as well smack it." I don't think scoring 25 yard freekicks ourselves are the problems. Defending crosses would be a nice start. Or creating clear cut chances.