I think that socializing naturally inhibit's a person's ability to think for themselves.
I don't mean that in a "durrr you're all sheep" way, but in the sense that when you spend a lot of time being forced to act in accordance with a group, you have to limit your personal agency, you often have to accept the beliefs and values of the group as your own, so you will feel less likely to need to think up any new ideas of your own.
When your life is governed by the group, by social norms, you never have to think about what you should be doing with your time or why you should be doing it, because the group's rules have already laid out the guidelines of all of this for you.
If you don't need to think as an individual, your mind will have less excercise, and as it weakens from disuse it will be less capable of independent thought.