What is the primary advantage of using one-letter amino acid codes over three-letter codes?

Why is the one-letter code 'C' assigned to Cysteine?

Given that both Leucine and Lysine start with 'L', why is 'L' assigned to Leucine?

In the protein sequence 'MKWV', which amino acid is represented by 'W'?

What is the one-letter code for Phenylalanine?

What is the benefit of using the mnemonic 'nerdy WQF'?

Why is the one-letter code 'A' assigned to Alanine despite not being unique?