People in all religious groups are joining for a variety of reasons. One of these, in all situations, not even all Christian situations, is certainly to be part of a crowd. It is necessary for the priest to help a person see that in the end their decision to join the Church must be rooted in a desire to be united with Christ.
But since no-one tends to have entirely pure (in the sense of simple) motives, it is the case that a person seeking Christ will also often join a particular Church because they are friendly, they are a family, or more negatively, because they are a tight knit group resisting the world.
I would not say that most converts become Orthodox because of a group mentality. I would say that it is generally much too costly for that to be the prime motivation. And as a lasting motivation it is problematic because people will always let us down. I would probably want to say that it was more relevant a motivation in the case of modern non-denominational protestant groups, especially those shading into cults.