The axons of lower motor neurons cover vast distances for their size. From the spinal cord to the muscle is the equivalent of a tube train travelling from London to New York! Transporting the necessary proteins from the cell body in the spinal cord to the nerve terminal in the muscle is therefore an onerous and energy-consuming task.
If you were to cut a peripheral nerve in cross-section, neurons of all types (motor and sensory) would be seen tightly aligned. The wider ones are the lower motor neurons, able to transmit signals at the fastest speeds.
As axons reach the muscle, they begin to branch off in order to connect to many muscle fibres simultaneously. These projections are long and plentiful, enabling a single motor unit to cover a large volume of muscle. This ensures the force generated by a single motor unit is sufficiently spread out.
Lower motor neurons have the capacity to create new branches to compensate for the loss of neighbouring motor neurons. This sprouting process has evolved as a protective mechanism, so that the connections with muscle fibres can be maintained. This helps to maintain muscle strength despite the loss of motor neurons.