Pet Peeve - Failure to Acknowledge

We all have them.  I am sure there are some we share in common with each other.  Some are unique to us. 

My colleagues at work can probably rattle off my pet peeves without much thought.  I have a feel for some of theirs. 

One of my biggest peeves is when you encounter someone in the elevator, look them in the eye, they look you in the eye, you say "hello" and they say nothing.  I used to think that I just did not speak loudly enough for others to hear.  Or, I would rationalize that they were probably thinking about their job, their e-mail awaiting them, etc.  Then, one day I encountered someone in the elevator who said nothing to acknowledge my "hello" only to see and hear them animately greet someone else when the elevator stopped at another floor and got on.   Then, it occurred to me that people actually feel either too uncomfortable or too good to say "hello" while in elevators.  I have no other explanation since eye contact was made. 

After all these years, I have not figured out how to respond to these non-responses.  Typically, I just ignore the slight.  What I have decided, though, is that I will go out of my way to acknowledge anyone who says hello to me on the elevators or in the hallways, etc.   I cannot control the behavior of others but I can control how I respond.