I'm far from an expert on these matters but my understanding is that using capital letters to start sentences is done because it helps anchor the reader's place

I'm far from an expert on these matters but my understanding is that using capital letters to start sentences is done because it helps anchor the reader's place in the text. When capital letters are excluded, it's easier for a person to lose their place while reading. There are other ways this could be accomplished such as returning to the old custom of using two spaces between sentences or making sentence ending punctuation marks larger or heavier, but initial capital letters is the one English has settled on and is almost universally used.