In most cases, interns tend to interact only within the functional area they work for and ignore others. Two reasons to interact with other functional areas:

To learn about the culture of the company: It is necessary to understand the relationships between different functional areas. Often times, different functions within a company have competing goals and have conflicting milestones. For instance, marketing and finance departments usually have different opinions on product launches. So it is a good idea to talk to all departments to understand the big picture. After all, it’s not guaranteed that you will end up in the same department when you get the full time offer.

To learn about the opportunities that are available in other areas: Hopefully you will do well in your internship and receive a full time offer from the department you worked with. In some situations, it may not be feasible to get the offer from your departments even if you did great in your internship, for various reasons that I will not elaborate on in this post. So interacting with other departments and building connections will help you apply for the opportunities that are available in those areas. If nothing, this is a good way to build your network and this may even create a unique opportunity to find your mentors.