co-workers are in many ways competition, revealing certain things to them can be bad for your career. And I'd bet that most people hiding things aren't murderous, just struggling.
I don't know where you work, but I have never held a job in ~25 years where I considered any of my coworkers as any sort of competition, and actually quite the contrary, either camaraderie or at the worst, a lack of interest due to e.g. no common interests. I have the feeling that my coworkers always felt the same... perhaps I should ask around.
I've rarely met people that let it hurt the camaraderie of the team (I have met them, rather cut throat people, but not often), but when there's three of us in a role and one spot we all want opens up - we're absolutely competing for it.
