Watches? Jewelry? Monogrammed clothes? Custom-printed shoes and t-shirts? Lots of examples, and of course it affects resale.

Apple was clearly thinking outside the category of “consumer electronics.”

Many people don’t care about resale or pass-along value in the things that they own or gift.

And even if one does, then you just consider the diminished value as another cost of having the personalized item.

For many people, especially gift givers where the item is about far more than economics, it is worth it. And it is very unclear to me why "resale value" should trump about a million other considerations.

I engraved mine for two practical reasons — tell mine apart from others and have contact info in case I lost it and it was found by a decent person.

This was very much a thing. The emotions wrapped up in iPods back in the day are incalculable. It was the tool that set us lumpenproles free back in the day

I don't recall any other company offer such service for consumer electronics.

Then recall that premium silver, especially items given as presents, are very often engraved, and have been for hundreds of years.

Apple is a premium brand, not "any other company," especially in the era this post covers.