Wait, shouldn't the stronger rider carry the heavier load and ride with or behind the slower rider?

If you are the slower rider it can be a very enjoyable experience to have someone to accompany you and encourage you to try harder. The stronger rider can relax and enjoy the scenery. A slow ride is better than no ride.

Excess weight sucks, ask any tourer that has mailed stuff back home. Or any rider that has lost weight from riding. A lighter bike does feel different, even if it isn't much faster. That psychological factor alone is a key selling point behind most bicycle equipment.