This is a quality that serves a purpose, it keeps you from rushing into things, prevents flights of fancy, stops you in whatever way and/or brings pause because if doubt arises you realize that you don't really know, do you? Not for one hundred percent certain.
Where there exists doubt, there also exists examining methods and means concerning the factors that run machinery, processes, people. Let's look at people.
When there is even the tiniest shred of doubt concerning other's true course, there is room for mistrusting their motivations, their judgement, their affiliation with you, and their loyalty.
Trickling down from the top, trust must be established so that loyalty can survive any test, this trust is built on reputation, and reputation is built on integrity. Doing the right thing, it is often called. Now, the right thing could actually mean the wrong thing depending upon which side of the fence you are on but the key principle is integrity. What they in the olden times called honor.
In the polarized environment we have at the present, that which will continue to stand will be the side where trust is well established, loyalty permeates the organization, and the organization itself, big or small, is an honorable environment in which to serve. If these qualities are in doubt, exit strategies are secretly planned by everyone working there.
Where doubt exists there also exists fear. Those flickers of fear can be fanned into flames. Not the environment you want to be in as shaky foundations tend to collapse abruptly.