These figures seem way off. Horses do sweat like humans, and their upright stance similarly saves energy. Wikipedia says 14-15 hours for 100 miles.
Compare apples to apples, though. Horses run these times assisted by humans. Horses eat grass (they don’t hunt for survival), a time-consuming food to ingest & digest. Horses don’t appear in some environments (humans are the most adaptable large animal, partly because of mobility); even when they do, they need human care.
Most of all, two legs is a disadvantage in a sprint but unstoppable over a long enough course. Humans are self-sufficient, omnivorous, but most of all have hands & can make & use tools. Humans can forage & eat & drink without stopping or even slowing down much; additionally we make portable containers for food & drink.
Humans are well aware of their advantage in nature & take care to practice & fabricate the necessary items in advance. Horses can make us work, but we would eventually wear them down.