Why do we need to write "I" with a capital letter?

One of my students asked me this the other day.... Excellent question, but I didn't know the answer. Fortunately we have "Google" and everything can be found on the web. So here is the answer:

The Barnhart Dictionary of Etymology says:

"~I~ pron. 1137 i; later I (about 1250, in The Story of Genesis and Exodus);
developed from the unstressed form of Old English (about 725) ic singular pronoun of the first
person (nominative case). 

Modern and Middle English I developed
from earlier i in the stressed position.  I came to be written
with a capital letter thereby making it a distinct word and avoiding
misreading handwritten manuscripts.  In the northern and midland
dialects of England the capitalized form I appeared about 1250.
In the south of England, where Old English ic  early shifted in
pronunciation to ich (by palatalization), the form I did not
become established until the 1700's (although it appears
sporadically before that time)."


http://www.alt-usage-english.org/excerpts/fxwhyisi.html

Why is "I" capitalized?

http://www.alt-usage-english.org/excerpts/fxwhyisi.html

Image source: https://descriptivewords.org/letter-i-list-of-descriptive-words-that-start-with-i/