No idea why Apple, one of the richest companies in the world, and "all about the customer" needs to place a hold on my card for a warranty replacement. I've exchanged a faulty $3,000 camera on Amazon and they overnighted the replacement, and said that if I didn't return the faulty one within 30 days they'd charge me. They didn't pre-auth or hold funds.
In order to get the replacement, I needed to know the serial number of the AirPods but didn’t need to provide any proof of purchase (I wasn’t the original buyer of the AirPods). This suggests to me that anyone who can get AirPod serial numbers could get free AirPods sent to them by contacting customer service. Absent the credit card hold, it seems like a good way to steal a lot of AirPods. I would guess at Apple’s scale, someone probably has done this scheme in the past so they need to find a way to prevent it (even if it never happened with AirPods, it probably happened with iPhones). Asking for the credit card hold upfront is a little unfriendly, but a lot better than dealing with a bunch of anti-fraud/collections work. It’s also much more friendly than requiring the customer to send in the broken AirPods first to get a replacement (this is the most common repair service I’ve experienced from other manufacturers, and it’s painful enough that I usually just try to fix the thing myself or throw it away).
I’d say the credit card/mailing method is also not Apple’s preferred means of exchange - it’s the backup for when the Apple Store is unavailable. At the store you hand them the AirPods when you get your replacement so there’s no need to provide a deposit.
Better hope you have a credit card, I guess.