Humans are naturally different and diverse. A curriculum which is the core of the standardised education system doesn't address the diversity of human intelligence and often, only enjoyed by certain types of students.
Secondly, human beings are inherently curious if you are wondering whether students learn without being forced. We all have different passions but left to our own devices, some of us may not ever discover and pursue them. If teachers can light students' curiosity, they can learn with little if not without any assistance very often as we, especially children are natural learners.