This question looks irrelevant at first perhaps, but it will tell you a lot about the corporate culture of the organization. You should direct this question primarily to the hiring manager and ideally a coworker. They will be able to tell you what they do in the team you will be working. The human resources representative could tell you about the corporate wide trends, but would not be able to tell you exactly what your team does.
Matching Personal Lunch Habits: The jury is out on this one. People are just different, so what if some like to eat lunch together and others want to grab a quick sandwich at their desk, while others tend to find their own circle to eat lunch with. You, on the other hand, may be irritated by the person who always insists on talking business during lunch as well. Furthermore, some job roles do not allow this as the team members are often on different locations or eating with the customers. In reality the most important goal with this interview question is to match the team behavior to your own preferred method of operation. For most people the relevance of this goal can be questioned. There are other factors such as salary and expectations that are much more important to you.
Understand Corporate Culture: In a true team environment, people would most likely not be having lunch separately. It would be understandable if this is more of an individual contributor type of environment.
Neglecting to Consider the Corporate Environment: A very social corporate culture could have people connecting here and there within the organization, thus making it possible to have lunch with different people every day. This is probably to be preferred before an organization where everybody just sticks to their own teams.
All Questions to the Hiring Manager at Job Interview
All Interview Questions for the Co-Worker