Have you ever seen someone with an expensive watch, a Rolex, Panerai, Omega, etc with a protector on the glass or a full body protector? No, of course you haven't and they're far more expensive and will last far longer than an Apple Watch.
1. Those watches all have sapphire crystals, so they aren't going to get scratched. Not the case for the Ion-X glass.
2. I'd be willing to bet if someone made a protector for the body of those watches, some people would buy them. I've seen people with their own homemade solutions to this issue in the absence of a market for such things. Also, if you can afford a 5K-10k watch, it's often the case that people don't worry as much about minor to modest damage to personal possessions because you more often have plenty of disposable income to replace or repair at your leisure. Someone putting a protector on the screen or body of their Apple Watch is very unlikely to be the person who also owns a 5k-10k or greater watch. We're talking about two different populations here, and one is not wrong while the other is right.
3. Luxury watches are supposed to be serviced periodically, and with those services you can choose to have the case and bracelet refinished to brand new condition.
4. There is something counterintuitive yet still compelling about keeping something in good condition that you know you will only have for 2-3 years, as opposed to something you expect to keep potentially for life. You know that it's possible to keep something you'll have for a short time in perfect condition, whereas something you expect to have for decades, you know that's impossible unless it becomes a "safe queen," so it almost seems more natural to allow the so-called "wabi sabi" or patina on a very expensive watch to happen so as to add character. All of this is not necessarily logical, but such is the case.
