alt Hacker NewsThere's approximately three possibilities that could lead to you believing that. Either you haven't formed close relationships with such people (unlikely), you lack the awareness to realize who they are, or you are one yourself and lack the self awareness to recognize the patterns.
Obviously some people get addiction problems, and obviously some people are more vulnerable to develop them than others, but I can understand the reluctance to ascribe that to their personality.
Why can't it be the situation? Even to call it the internal situation if you find no obvious external reasons, is probably healthier than to ascribe to the essence of who you are.