Why are most food chains limited to three to five trophic levels?

Most food chains are limited to three or five trophic levels because the energy available is only enough for those number of trophic levels: there is insufficient energy to go round more trophic level. At each trophic level, a large quantity of energy is used to maintain organisms at that level, because of this, organisms at one trophic level, pass less energy to the ones at the next trophic level.