In the context of students, Prime Student is 50% off. It appears to still be that way. This built up a lot of loyalty for early Prime members who were students. That loyalty appears to have continued for close to a decade for many people.

Remember that way back when it was business as usual to pay $10+ for shipping if you bought online. This meant that if you bought online more than 4 times throughout the course of an entire year, you were ahead. It also allowed you to buy at any time without worrying about the minimum purchase total, increasing buying frequency.