The difference between touring on a motorcycle and touring on a bicycle is that, on a bicycle, YOU are the motor and you will be the one who has to move whatever you load your bicycle with. Any backpacker or cycle tourist will tell you that it's very tempting to fill up whatever storage space you have "just in case" you need a particular item, with the result that you end up hauling twice as much weight as is really necessary. I should know, I've fallen into this trap too many times.

A heavier load on the bicycle means more weight for you to haul around, and more wear and tear on tires and spokes. It also makes the bike harder to maneuver in traffic or around obstacles, and makes controlling your speed on downhills harder.