Of course, the ride wasn't free; after all, even mules and their drivers serving the people need to be well-fed. Thus, regardless of age, except for infants under one year old being held, everyone else was charged five cents per head. The things you brought couldn't be too many, either; if you had extra, it would cost the price of another person's fare.
And the cart only left when it was full. It made just one trip a day and didn't operate on rainy or snowy days, or during busy farming periods. A mule cart could carry no more than six people at most.
Five cents might not seem expensive, but a round trip was still ten cents. So, not many people were actually willing to pay to ride; many preferred to go on foot.