Well, there might be many people who may be reluctant to trust their co-workers. This is because the workplace politics might be a huge factor why co-workers may have a really harder time trusting each other. This is a major problem faced by many people in their workplace.
I'm completely reluctant to trust any of my co-workers that I haven't vetted to be someone whom I can count on. When the least people you expected in this life turn out to be the one's that betray you, all manner of trust in you will go into lock and key.