Question: Why does Apple provide free engraving for its earphones (AirPods® and other variants), tablets (iPad® and variants), and other products? [ref]
Answer: Because the engraving reduces their resale value, which reduces the resale market’s supply, which increases new product sales thereby increasing profits.

Welcome to Costs Matter, a series that asks different questions all of which have the same answer: to better manage costs. The costs are frequently economic though not always. The series focuses narrowly on the impact of costs. It does not claim these costs are the sole cause. To read more in the series, visit https://medium.com/galileo-onwards/costs/home.

In addition to the reduced resale value of an engraved iItem, Apple also imposes more restrictive return and and exchange policies against them. See https://www.apple.com/shop/help/returns_refund for details. Below is a screenshot in case they change their policy in the future:

Screenshot taken from Apple’s website at https://www.apple.com/shop/help/returns_refund. Copyright Apple.Generated by author. License: public domain.