Watches

I was looking at a 37mm watch recently, that is 13.3mm thick. I have a 5.5" wrist, so that's just going to be unwieldy and look disproportionate.

I don't think so. A few folks really want something thin that can easily fit under the cuff of a dress shirt. And most of us don't want something so thick that it looks like a metal ingot on our wrists . So with that in mind like 10-12mm is the sweet spot for most people. But yeah some folks worry about it too much, for instance they'll prefer a manual wind movement to an automatic one since it might allow the case to be a mm or so thinner, and they'll lament watches than come in both auto and manual and the manual versions aren't any thinner.

Very few designs benefit from being thick, and the opposite is also true -- most designs improve by being thinner. So yes, thickness of a watch (and the ratio between case width and thickness, and also lug-to-lug distance) is a relevant selection criteria.

I'm only concerned about watch case thickness if it's enough to get caught on shirts, jackets, dense undergrowth, and those sorts of things.

Thick cases are generally heavier and I feel them more when I move my arm/wrist. I like to forgot they’re on

Enthusiasts are over-obsessed with size, in general. Look at how many posts there are nervously asking if a watch fits. "I'd love this watch if only it was 40mm instead of 41mm!" Give me a break.

Size on its own is neither good nor bad, neither too big nor too small. It depends on context. I'm currently wearing a 17mm thick TAG Heuer Carrera, and it's delightful. A 17mm thick dress watch? Hard pass: It would never fit under a shirt cuff. So many people think that there's some sort of universal ideal size, but it really depends on the design of the watch, the size of the wearer's wrist, and the type of fit you want. This Carrera would feel silly to me if it was much smaller.