If we look at just the average of 4-6 pounds that comes out to being about the weight of a half gallon of milk. If you are out for part of the day or even the majority of the day that weight will eventually wear on you and become challenging. If most people were told they need to carry around a half gallon or sometimes a full gallon of milk all day, most would probably say no way. Some would do it but would likely being in pain or discomfort by the end of the day.