Why do food chains generally consist of only three or four steps?

(N/A) According to the $10\%$ law of energy transfer, only about $10\%$ of the energy available at one trophic level is transferred to the next higher trophic level.
Because so little energy is available for the next level of consumers, food chains generally consist of only three or four steps.
The loss of energy at each step is so significant that very little usable energy remains after four trophic levels to support a fifth level.