
It's not easy to stretch outside your comfort zone. After all, it's called a comfort zone for a reason. Outside your comfort zone is pain. And you're built to avoid pain.
It's only natural to resist the things that don't line up with your personality and preferences. You could call this one of the default settings of being human. And so we tend to surround ourselves with people who help us avoid the pain of the stretch. It usually takes a dramatic shift in our circumstances (marriage, career transition, children, relocation, illness, etc.) to press the urgency of growing beyond our comfort zones.