I have been teased many times over the years for carrying more stuff than I probably need, or at least more than most people bring, on my long distance rides .......... and yet I have NEVER used a pannier on a century unless the century occured on one of the days of a loaded tour. I've never used a pannier on any of my long rides, including 1000K and 1200K randonnees!! I reserve panniers for touring.
On most long rides I carry a handlebar bag which contains food, medical supplies, and other "personal" items (i.e. camera, money, ID, etc.), and a bag on the back of varying sizes depending on the length and conditions of the long ride. The largest bag I carry is my Carradice which might contain tools, more food, a small bivy, and clothing for really long distance rides. The smallest I'll carry is a little bag with tools and a couple articles of clothing for emergencies.
However, I too am curious why you didn't ask someone what they were carrying. I've been asked many times about my choices for set-up and gear, and I've asked others about their choices. The answers can provide us with a different way of looking at things, new ideas, new choices.
