Completely spit balling here but wasn't the abstraction of your cursor originally a finger? If so the 45 degree tilt with the 'finger' pointing to the left make

Completely spit balling here but wasn't the abstraction of your cursor originally a finger? If so the 45 degree tilt with the 'finger' pointing to the left makes sense if you just reach out with your right hand and point at something on the screen. At least for me when I'm pointing at a regular computer monitor my hand is tilted not strait up and down.