we still write / read vertically sometimes. for example, japanese newspapers are still written like this : ↓ 　　↓ 　　↓ 　　↓ ↓　 　↓　 　↓　 　↓ ↓　　 ↓　 　↓　 　↓ 　 　 ↓ 　　↓　 　↓ 　　 ↖　 　↖　 　↖ until the world war 2 ended, we wrote horizontally like this : ↘←←←←← ↘←←←←← ↘←←←←← 　　 ←←←← but now we write like this horizontally : →→→→→↙ →→→→→↙ →→→→→↙ →→→　 i hope you can see what i wrote as i intended with your device ...

I think this is more like personal preference. Not many young people write personal letters and memos vertically anymore, but it is still common amongst elderly people. They believe it is quicker to write because it is easier for them to write cursive script. On the other hand, most published books (novels, dictionaries, mangas, etc.) are still printed vertically. Also, there are applications to change text vertically for smart phones. So, I assume there are enough people who still prefer to read books vertically thought they write horizontally themselves.