How do you start answering the phone? You may say hello or perhaps you would rather use your name. Anyway, which one makes your audience glad as they hear your sound?
Suppose that your best friend sent you a letter full of many warm and kind words. However, he/she missed their hello at the beginning of their note, instead, they started with your name and addressed you as their dear friend. You might have felt a little bit sad while reading your friend's letter with out hello and simply seen a huge gap amid a large number of letters.
Having experienced, You met someone else for example, another your friend somewhere and heard everything from his mouth but saying hello. You may here consider them a little rude and impolite.
Saying hello is very short, however, it conveys an ocean of messages based out of your heart and mind and indicateds somehow your polite manner.
You can try how saying or omitting hello can impress on your audience, and also how your hearers send their reflection to you as a mirror in which you see yourself.