I can see several reasons why this may be done, and most depend on the retailer and product. The short version is that restocking fees make sense for large or valuable items, and for small businesses.

High-value items like electronics, jewelry, etc. are prone to theft and return fraud. For example: someone could buy a computer or jewelry, swap some parts, and return it with different parts that are worth much less. It takes time and resources to test the product to verify it’s the same as what was sold.

Large items like furniture are very expensive to ship and when one is puchased, the retailer would often restock the item which costs them money.

Small businesses are often charged higher fees by manufacturers and distributors for ordering or shipping products, as they generally don’t order in high amounts. This means that they will make less money if they sell an item for the same price as a large corporation. Small businesses also don’t have the same resources for testing returned products, so processing returns has a much larger impact on them vs large corporations. Because of this, it often makes sense to implement a restocking fee to make up for these costs.

Large corporations generally have a streamlined process for processing, testing, and shipping returned products. While some things are still expensive to process, it’s significantly less impactful for a large business to process a return. It still costs money to process a return, but in my opinion restocking fees can be greedy for larger corporations that can eat those costs.