The reason that it is important for students to be engaged with their studies is that they are much more likely to succeed if they are engaged. Since college performance is important to one's future prospects, engagement in one's studies is extremely important.
When people get to college, they are typically facing an academic environment that is much more rigorous than any they have yet faced. At the same time, they are faced with a social situation with more freedom and temptations than they have had while living at home. Since the work is more difficult and since it is more difficult to concentrate on that work, it is vital that students be engaged so that they can have a better chance of doing well in their classes.
It is very important because your life, career depends upon this stage of studies. You have so much studies that if you are not engaged with it and you do not study properly, you cannot complete your studies.