"When the XEROX PARC machine was built, the cursor changed into a tilted arrow. It was found that, given the low resolution of the screens in those days, drawing a straight line (left edge of arrow) and a line at a 45 degree angle (right edge of arrow) was easier to do and more recognizable than the straight cursor."

Well there ya go right there. The left side of the arrowhead is a nice clean straight line, and the right side of the arrowhead is as close as possible to 45 degrees, cutting down its "jaggedness".