The beauty of inline quoting is that if you don't see a need to use it then you don't. It is in no way arrogant to suggest a method of replying which is unambiguous. Nobody is suggesting that it is used in places in which it is not necessary.

I hate to think of the hours wasted due to ambiguity in email replies. More often than not people end up using the telephone or meeting in person which wastes even more time rather than learning how to be clear. I don't understand why all effort to be clear and precise goes out of the window when dealing with email.