reasons why cliques at work are bad

Cliques usually don’t socialize outside of their group.
Excessive togetherness is bad for companies because those on the outside become distracted and dissatisfied with the work environment. They may even expend more energy trying to cope with the clique than they do on their actual job. What’s more, cliques can become more about the group than they are about the company. In the end, this impacts the company’s bottom line. And it causes good employees to flee the company when they have had enough.

Cliques thrive when no one addresses their behavior.
It is important to address issues with cliques as soon as they occur. When you see something inappropriate, be sure to address it right away. But try not to overreact. While it is important that there be unity among all workers, you want to be careful not to punish employees for having close friends at work.

Be sure you know the difference between a clique and a group of friends before you step in and break them up.

Cliques often ostracize or exclude other employees.
One way to prevent employees from ostracizing others is to assign them to group projects instead of allowing them to choose their own groups.

When you allow employees to pick their own groups, you are opening the door to workplace bullying. Conversely, when you select the group, you are ensuring that they include those outside their circle of friends. Pre-selected groups also give employees an opportunity to learn how to work with different types of people.

Another way that workplace cliques can affect employee morale is by making a big deal out of the things they do together. For instance, cliques often laugh and share inside jokes that other employees do not get. These secrets create an unbalanced workforce because some employees are left feeling like outsiders instead of part of the team.