Why is it so hard to say "Hello"???????

I have thought about this a lot so I am gonna put it on here and then stop wondering or thinking about it. I thought the saying was "it's so hard to say goodbye." But I am beginning to wonder if it is.... "it's so hard to say hello." I don't just mean when you see someone you don't know at all, I mean people we kinda know..........we walk by people (even people w/ so-so know) w/ out saying a simple hello. Or worse yet, we avoid people just so we don't have to say hello (don't act like I am the only one who has done that heheeheee). I don't know if the problem is everyone is waiting for the other person to say hello first or if they are too busy to say a quick one word while passing you by. Or another reason for why people don't say hello could be b/c they just don't want to. I am going to make a better effort of saying hello....just hello. Nothing attached to it, just a simple hello.