There's also the interesting question of language differences. While a single letter might have been good enough for Latin, Italian, French, etc. German has a s

There's also the interesting question of language differences. While a single letter might have been good enough for Latin, Italian, French, etc. German has a stronger need for three, as shifting pronunciation of "v" as a consonant to become practically the same as "f" strangely wastes a letter and requires a new letter (which turned out to be "w") for the old sound. Meanwhile, German also has "u" and "ü" as vowels.