watch-er,
The case you allude to, with which I am thoroughly familiar, is a rarity. The vast majority of armed robberies occur at night, in obviously seedy or isolated environments, and involve a low "score." Moreover, the bad outcome in the case you allude to might well have been prevented had the victim followed the standard guidance to comply with the man with the gun, rather than challenging him and struggling with him.
If you avoid alcohol, drugs, isolated areas, and high crime areas, your odds of being attacked for your watch in a large U.S. city are so low that insurance against this risk at 1% of replacement value per year is not a rational investment, unless perhaps you flaunt a colored gold bracelet.
Park