Welcome to this little corner of the world.
Why do articulated grader frames articulate in the manner shown in your photo????????
Will, " 'Cos they can", do for an answer??????? Hmmmmmm. I didn't think so. Jeez, some people are hard to please.
Well, being able to articulate the frame in the manner shown enables the operator to position the drive's line of thrust directly behind the greatest load on the blade, helping to keep the grader travelling in the direction required and reducing slippage, both sideways and in terms of traction loss.
Other uses for this sort of articulation are to enable keeping the front wheels on smoother ground by placing them on the previous grader pass and allowing the front wheels to be put up on a batter while keeping the drive down on flat ground.
Now I'm so tired after all this typing that I'll have to take my weary old bones and and have a nanna nap. G'night, to you and Grader4me.
And do you really know all the reasons why grader steer wheels tilt/lean? Maybe, if you haven't yet read it, you need to go back and read the posts on this thread: