Could be a policy coming from the top. Many tourists think in terms of "Mexico" not the various parts of Mexico, thus all the "is it safe in Cozumel" questions because there was a rash of violence in Acapulco. The overall image of Mexico is affected by all parts of Mexico.
All ^ true. I recall it being a constant uphill battle trying to explain to folks, from family and friends back in the states to tourists fresh off a boat, that the whole Mayan Riviera,and Cozumel in particular, were well policed and extremely safe, requiring no more than the same caution and common sense you'd apply anywhere back home.
That being said, I have a photo around here somewhere taken by my brother, of me lounging in a hammock, reading a local newspaper, with the giant headline, "US TOURISTS GUNNED DOWN IN CANCUN !"
That day (around '93) ,we had just hopped a bus in the (Cancun) hotel zone, right across the street from Aqua World and Gypsies restaurant, and just a little while later, a car load of gangsters pulled up and sprayed the restaurant with gunfire !! (reportedly, a drug-related hit).
But, other than a couple home break-ins, and an attempted bike theft, my experience with crime down there was virtually nil. Heck, I got shaken down by the cops more than anything else, LOL!