Why horses were so important back in the day?

 So, I published my fourth book. It's a stand-alone short novel about a bounty hunter taking his bounty across Rumelia. During their journey, you would find that a horse is regarded as an important transport. 

There weren't any vehicles with engines back in the 15th century. As a horse could make 40 to 48 km/h (4.9 to 29.8 mph) on a single run, they have become the most reliable animal as a mode of transport. We can find them as a bareback vehicle or a cart-puller.

Do you have more knowledge about horses? Feel free to comment down below.