Most Roman script langauges use capitalization to make it easier to read. By capitalizing the first word of a sentence it makes it easier to locate the start of the sentence. By capitalizing proper nouns, it makes it clearer what (or who) you are talking about. People raised as Anglophones fine the semitic languages lack of capitals to be annoying.
That’s true. It’s a convention. And we should try to be conventional.
Because we are used to it, it makes it easier for us to read. Obviously, if you have something you want to say, you would want to make it as easy as possible for people to get the message. Capiche?