It is not mandatory, of course. But writing a review on the online site is like doing community service. Suppose you buy any Demon Slayer earrings from any of these sites; customers often purchase with trepidation. Writing a review about your experience with the product(s), even if it is good or bad, attests to the fact that you are making your fellow customers aware of your experience with the earrings. Following this, it is up to them to decide to purchase. But doing such a task often leaves a good impression on the purchasers.