As we all know, in English the first person singular is the word I. Why is the "I" in that word being capitalized? Why not the same thing happen to the letter "M" in the word me or "Y" in the word you? We may say that this is a symbol of egocentrism but this is not really the original reason why the letter "I" is being capitalized.
In Middle English, the original first person singular was expressed with the word ich which eventually shortened to i in lowercase. However, the printers in those days found it difficult to print the word i without accidentally joining it to the words that preceded or followed it. Therefore, they managed to capitalized the letter "I" to make it stand as an isolated word and that is why we used capitalized "I" in the word I nowadays.