Why is a pyramid effective for showing energy flow?

It shows how energy transfers from one organism to another and the amount of energy lost (10%) as the pyramid goes up

The other 90 percent of the energy is needed by organisms at that trophic level for living, growing, and reproducing. This relationship is shown in the energy pyramid above. It suggests that for any food chain the primary producer trophic level has the most energy and the top trophic level has the least.