This is so simple but true, if sellers would only listen.

I think a high price is the most common reason by far, but certainly not the only one.  I once was the fourth agent.  I had them send Fang, the Realtor-eating hound, off for a vacation to Camp Waggy.  I raised the price by $40,000, put a lockbox on the front door, held an open house, and by the end of the Open had five offers, three above the list price.  It's important to look at the big picture.

True. I have one like that now...eventually this market will come to it though.

Richard Weisser - Normally I wouldn't disagree with what you have said. But I have found by personal experience that all it took was marketing the home.  This has happened more than once.  As the second agent, I always take professional photos and vrtual tours.  Two homes had accepted offers in one week. So unless you consider that you are adding value by better marketing. I would have to say that there are exceptions to your premise. 

Richard, you have not lost your touch.  We need to see you here more often my friend

Amen.  Richard you are correct.  It's so simple really.