The dangerous thing is that you can, in many science fields, get a PhD with minimal collaboration. Just pass the quals and focus on your disseration project, there you go. But you’ll be at a tremendous disadvantage during a faculty search, when you’re up against all those people who did internships early in their career, kept those research connections, led research projects in the local lab, joined student groups at conferences and helped organize a student workshop, reviewed for conferences, helped out on projects with people you met at conferences, contributed to funding proposals, etc.