I can give you a few reasons.
My first use case was when I was creating a close icon where you have an X inside of a circle. The icon was a total of 16 pixels. When I drew the lines they were not perfectly centered. But interestingly they were already positioned at half pixel positions.
When I used the center alignment tool and the center command I noticed it was not accepting half pixel values but I could set the position with fractions through the properties panel. If you use the line tool now you’ll see it positions on fractional points.
You also have the option to set the position of the stroke (inner, outer or center) so you won’t avoid sub pixel values or positioning.
With hi dpi devices sub pixel values are not blurry anymore since on 2x devices there are 2 dots for 1 pixel (144 / 72). So .5 value lands on one of those pixels.
Finally, if a graphic is on a half pixel when exporting renditions and scaling up the graphic will be placed accurately on full pixel.