Beyond the observational evidence: that fact that every culture to ever exist in all parts of the planet value some degree of conformity, the conceptual points are just as strong: efficiency, harmony, unity, happiness and many other traits are higher in more uniform groups.
What if everyone in the classroom spoke a different language? What if everyone in the classroom had a different set of values and ethics? These commonalities ARE a degree of conformity, and they made interacting and the rules of engagement clear and simple so more important things can be focused on.
Obviously there are drawbacks: if everyone was the same person then there’s nothing new. One could argue that everyone having the same religion is worth it because now everyone has more in common to agree on, one could argue that removing that freedom comes with too high a cost to the new and interesting.
In summary, conformity is certainly useful, but comes with side effects and drawbacks.