Why mathematicians are obsessed with this luxury chalk [video]

I think the video referred to is available on Youtube: https://www.youtube.com/watch?v=BORVxbsdkCM

We write a lot in the blackboard durig a class! I sometimes arrive to a classroom after another course and ser only a few words written and the feeling is very strange.

The supply department makes friendly complains/jokes because we use too many chalks.

Some of my coworkers even pay money to an internal unofficial found to buy better chalks because the chalks from the university release too much powder.