Remember, you can change the padding in Grid Properties. (This is the space between the node and the grid lines.)

One reason for doing this is to allow more room for a connector. For example, perhaps you want to add a label to the connector, but there is no room between the nodes unless you change the padding.

However, note that when you change the padding of a cell, you are changing it in Grid Properties, so it affects all the cells in the whole grid.