<p>Part of it is personal aptitude. It took me a whole weekend to write a 5-page literature paper, while somewhat who was a more skilled and prolific writer could churn it out in a couple of hours. As well, some students can read a 300p book in a day while others need half a week to do it.</p>
<p>Similarly, I would “get” Phys 7A-B after doing a few problem sets in a couple of hours, while others would have to read the chapter page to page, attend section and/or go to office hours.</p>
<p>I think it’s also true that most Americans have a hard time with maths and sciences, it’s partly a cultural issue. Many European countries like France or Russia have far more rigourous approaches to maths, which are drilled in students at an early age. </p>
<p>As far as the most time-consuming majors, it’s not just a question of assigning more work, it’s just that those majors are by nature more time-intensive. Debugging programs or building scale models takes a lot of time.</p>