It does seem strange. German, which capitalises every second word basically, doesn't capitalise personal pronouns, unless you you are directly talking to another person.
For example if I'm writing a (somewhat formal) letter (in e-mails or text messages between friends it doesn't matter), it would be something like:
"Good day, i
am writing to Y
ou regarding Y
our proposal blabla..."
It does look a little egocentric, the way the English language handles that, even if the hstoric explanation has nothing to do with anything like that.