Why search by starting letters?
Openings matter. In board games you often have to build off a tile already on the board, so knowing every word that starts with a given letter is a genuine scoring advantage. In crosswords, the first letter or two of an answer is frequently the easiest clue to lock in — and from there a prefix search reveals the rest.
Beyond games, a prefix search is a quick way to expand vocabulary, find brand or character names, or gather word families that share a common beginning like "trans", "micro" or "over".