Why cells are hexagonal while practically, they are circles?

A honeycomb of hexagons completely tiles an area, indicating complete coverage at the expense of distorting the shape of the cells. Circular tilings either overlap or leave gaps. A hexagon is to be taken as indicating a circular cell where the circle has the same center as the hexagon and a circumference passing through its vertices. The call of a mobile user passing through a grid of circular cells needs to be handed off each time the user leaves one cell and enters another. This has to be done by passing through the area where the cells overlap. At this point, the mobile phone is in the coverage area of two cells, the one it is about to leave and the one it is entering. In this way, the overlapping areas can indicate that the need for a hand-off is imminent, and the cell that is the target for the hand-off.