This page describes how to divide a circle in 8 parts. You will see that this is a lot more difficult than division in 12. Presumably this is a mayor reason that we still now are dividing days in 12 hours, the sky in 12 zodiak-signs, and the circle in 360 degrees.

Step 1. Start out with a circle, add a support line.

Step 2. You can now draw two other circles.

Step 3. The only reason for drawing the last two circles was to find an exact angle of 90 degrees for this new support line.

Step 4. Now you can draw 4 more circles.

Step 5. Only now you can divide the circle in 8. Note that the size of the circles changed 3 times. In ancient times this must have been a lot more difficult than division in 12.