Why are there usually never more than 4 trophic level in a food web?

Energy transfer between trophic levels is not very efficient, leading to a loss of energy as it moves up the food chain. This limits the number of trophic levels that can be supported in a food web. Additionally, with each higher trophic level, there is a decrease in available energy and biomass, making it difficult to sustain more than 4 trophic levels.