Newbie question about unlisted properties

[Omi C.]

Noob question alert - you've been warned!

I see a lot of posts about people finding properties before they hit the MLS, and how the properties that reach the MLS are the "leftovers" that the real investors didn't want. I understand that networking and marketing is the key to discovering these properties.

What I'd like to understand, however, is why any property owner would choose not to list their property if they are in fact trying to sell it. Wouldn't an MLS listing ensure the widest possible audience, creating the highest possible demand, thereby giving them the best chance at selling the property for a competitive price?

I'm just trying to understand whats actually going on here?

Omi