Answer:
because a lowercase i looks strange by itself
Step-by-step explanation:
"I" is a first person pronoun. Pronouns are words used instead of a noun. E.g You, they, them, he, she, we and I.
Nouns are naming words such as the name of a person, place, animal or things.
"I" is usually written in upper case because the lowercase "i" looks like a letter that detached from another word when writing a sentence.
Uppercase means capital letters while lower case means small letters.
