Letter frequency is vital in anagrams because it affects the difficulty and creativity of creating anagrams. Certain letters are more common than others, so they appear more frequently in words and phrases, making developing anagrams easier. On the other hand, less common letters can present a challenge when creating anagrams, as fewer words contain those letters. Awareness of letter frequency can also help create longer anagrams that use all the letters from the original word or phrase. Overall, understanding letter frequency can enhance the creativity and effectiveness of creating anagrams.