Because nobody cares about your diabetes and obesity. Lay down that taco and get some fricken exercise, FFS.
... possibly. Or they could be tomorrow's cancer patients, or tomorrow's stroke patients, or tomorrow's jack-knifed tractor trailer across three lanes of traffic patients. All those can happen to people without diabetes, too, though; it's part of living.
http://opinionator.blogs.nytimes.com/2012/09/25/bittman-is-a...
For those with Type 2, yes, exercise and eating right largely solves that (totally different) issue.