Two reasons come in my mind: 1. Some junior developers are just really good and learn fast compared to an average developer. 2. A junior developer has the energ

Two reasons come in my mind: 1. Some junior developers are just really good and learn fast compared to an average developer. 2. A junior developer has the energy and drive being new to the field. They are willing to do many things for the sake of learning which the senior developer is already jaded by.