Quote Originally Posted by zedeeyen View Post
Sorry mate, I don't even understand what you're trying to say here, and this is getting tiresome and circular anyway, so I'm going to leave it.

You originally asked "I wonder why many textbooks fail to explain that", and I tried to explain why. If you don't like my explanation then that's fine, feel free to invent your own one.
Ха! Я думала, что только я там ничего не понимала.