In today's world, students are exposed to an overflow of information. Our brain has a hard job to determine priorities. That's why we have to create stimuli that tells our brain:
This is important. Please remember!
There are several ways you can achieve that, but a very efficient one is writing about what you have just learned. When you write about a given topic, you draw on what you really know. Moreover, you develop your present knowledge into a more advanced version by connecting it to outside concepts. The more connections you can make between your many pieces of knowledge, the better you can retain and apply them. That is exactly what I am doing with this page. Since I do not want to forget my advice, I write about it and publish it to the world.
For the sake of being complete - Another form of supporting your memory is repeating information right after you have received it. Many people suffer from being introduced to people, and just minutes later, their names are forgotten. These situations can be quite embarrassing. A useful technique is repeating their names in our minds after we have been introduced...
Jeff is a nice guy. Jeff is a nice guy and he wears a funny suit, stimulates your mind to remember Jeff's name.
I shall also mention the power of mnemonics ( pronounced:knee monic) - for example, HOMES stands for the Great Lakes Huron, Ontario, Michigan, Erie and Superior. Will you ever forget again?
That being said, there is a difference between writing which you have done for a class, and writing which you have done because you chose to. Obviously, we are only going to voluntarily write about subjects we are truly interested in, or passionate about. And that is totally fine! After all, you should study what you truly care about.
One final thought about writing and education. In certain schooling systems it has become a habit to expose students to a minimum of writing. I don't care much about that 'fill in the blanks mentality', since it is not compatible with the reality of life. Tedious copying of sentences might seem redundant, but it is a perfect way to have something turn into second nature.