The article is just a bunch of fluff, this is the extent of its answer:

> We often crave self-definition and are attracted to group memberships that balance a sense of differentiation from the many with a sense of connection to people just like us.

My answer:

Most people don't have the wherewithall to give their own lives meaning. They need someone else to give them purpose. Being given a label and expectations, fills that hole in their psyche that they can't fill themselves.