My
God
I finally know why most fonts are broken, and it's difficult to distinguish 1 l and I.
On a portable typewriter, quite often there was not "1". Number rows started at 2, and where 1 would be, a key to ignore margins was. So how did they write "1"? That's what lowercase "L" was for.
source: https://www.youtube.com/watch?v=IsTjagrMBfI