A wearable called a Bag

When I went on my little walking expedition on Tuesday afternoon, I came across a group that I followed because of the observation I made about what they were carrying. They all had different bags!
A backpack, a canvas sling bag, a grocery roller and an overnight bag. If they were all leaving uni together and they were all conversing closely & laughing together as they were walking, would it be safe to assume that they might be doing the same course? Maybe the same subjects, timetables etc. So if they potentially needed the same things as each other for the days events, I wonder why their bags were all so different?  What else were they doing, where else were they going in order for them to select that particular bag for their walk? Do we choose a bag for comfort? Functionality? Or does it give us a certain sense of empowerment? How do these things effect our 'walking experience'?