Why do all Go board sizes have an odd number of lines? Why is a 19x19 board so much better than a 20x20 board?
Almost all go boards are x by x, where x is an odd number (e.g. 9, 13, or 19).

The point is to have the product yield an odd number of potential points. So that there would be an odd number of points in the game and a clear winner.

(In the Japanese counting style of "points," it is possible for both players to have the same number, but under the Chinese counting style of points plus stones played, the sum of the two players' results will be an odd number.)