Originally Posted by
dsbrantjr
"I don't know why they bother with direction arrow."
My uneducated guess may be that it has less to do with the tread and more to do with the direction the internal fabric plies are laid/overlapped when the tire is manufactured.
That was kind of my thought too, but I'm currently working on a bike with Schwalbe Land Cruiser tires.
They have opposite pointing arrows for <F-R>