When we were young, our teachers usually asked us to do the homework independently but things have changed as we grown up. Since we have to work together with our colleagues, working in groups plays a more important role in our lives.
Firstly, working as a team is one of the basic soft skills required by most of companies. Regardless of your major, you will need to communicate with other people like your colleagues and your customers. That is the reason why some companies usually create team-building parties and kick-off meetings in order to improve the relationships between their employees.