Why is the first-person-singular personal pronoun, I, always capitalized in English?

Ironically, it's an issue of tradition rather than grammer!

In Old and Middle English, the word for “I” was closer to its German equivalent “ich” and it was often spelled “ic.” However, the pronunciation changed over time and so did the spelling, losing the consonant c.

At first, the new word "i" was left lowercase. However, it began to grow taller than other words. By the time "Chaucer" wrote The Canterbury Tales in the late1300s, the personal pronoun "I" was slightly taller than its lowercase equivalent. From that point on, it was typically capitalized!