I haven't worn a watch since I got my first cell phone in 1996 as even back then those things could tell the time, so I no longer had need for a watch. I'm still not sure why I would want an Apple watch, yet, except maybe for easier Apple Pay use. In the meantime the wife and I each have an iPhone 12 mini, and while we have silicon cases I have not bothered with screen protectors. I tried screen protection on our SE's, which only served to reduce the response of the touch screen. I highly doubt I would add any extra protection to an Apple watch.
We regularly go on self-drive safaris in Africa, with our phones loosely lying around the vehicle, not a scratch. This is in a 1998 Landrover Defender, vehicles known to not have the most comfortable suspension. Then there is the dust in places like Namibia. And all the while I'm not at all worried about our €600 phones.
Now the only real reason I've put them in silicon cases is because the camera lenses protrude out the back, but we also like to lie them facedown, the extra silicon making them less likely to slide off whatever surface we put them on. The other reason is holding the phone, as without the case they can easily slip out your hand. This can be a bit of a problem when taking photos on cruise ships and boats. Either way I'm pretty confident these phones, watches etc are hard core enough to protect themselves to a certain degree without any extra cases.
Then I have a Nokia from 2005 that still works, this phone being pretty much indestructible right out the box....