Why is signaling in multicellular organisms more complicated than signaling in single-celled organisms?

Multicellular organisms need coordination between many cells whereas unicellular needs coordination only between a single cell and its immediate environment.

Explanation:

Multicellular organisms are the ones that are made up of many different types of cells that are organized in such a way there is a division of labor to form different types of cell that coordinate with each other to carry out different functions necessary for the survival of the organism. Unicellular organisms are the ones which are made up of only a single type of cell which is solely responsible for performing all the functions of the organism. Since in multicellular organisms there needs to be coordination amongst different cell types at many different events which may be very distant from each other, signalling in them is more complicated than unicellular organisms where the cell only needs to interact with its immediate environment.