i find the cross arm suits fighters who like to bully and can pack a strong hook. If you see Frazier or Foreman when they fight, they like to shove or manhandle (or at least foreman does) you, pushing you into striking range for a long hook, short hook. whatever.

And yeah you guys have good reasons on why the guard is flawed. It does leave openings, but thats what the low crouch bob and weave is for. You see Lamotta, Frazier they come in creeping in a real low crouch and when you overextend you jab or cross to reach their heads, pow, they come up with a hook.