Shared culture and norms are necessary for social harmony, and reduce the costs of law enforcement. Social harmony generally makes people happier as long as they are included in the mainstream, while internalized law enforcement frees up money for other uses. I see those as the main advantages of conformity.

I think however that it's generally true that conformity diminishes progress and positive change. Whether that's worth the loss of a shared culture depends. I think the current state in the US where there are two cultures which divide the population into two modes is harmful, since it makes society fractious and hostile. We could do for more conformity, now.

However if that were to shift back to a mass culture with various countercultures chafing against it, I think then more independent thinking would be good. I think mass cultures are the rule rather than the exception now, and most other places could do for more independent thinkers.