Plants planting Distance

Usually, the plants or trees grow and their canopy occupies a good distance in a circular way. While this is the norm, the distance between plants are given differently.

For e.g., in coconut, the distance is given as 25 Ft X 25 Ft or 25 Ft X 15 Ft.

The rows of the trees is usually bigger than the distance between each plant. My question is, if the plant or tree’s canopy is usually circular in nature, why this type of distance between the plants.

Planting in zig zag can answer to query.