I don't know, Bob. Part of me sees a devil-may-care attitude that says I've only got one life to live, I'm going to live it the way I want, by engaging in high risk activities, and eating what I want.
Another part of me sees an addiction factor involved. It's not to the extent of cocaine of course - one overdose of sugar or a knock on the head in a football game isn't likely to kill you, unless there are other confounding factors. (such as a diabetic dying from untreated ketoacidosis, or a football concussion so severe that it causes a deadly brain bleed) Basically, as long as the thrill (sweet foods that they love, or the adrenaline rush of participating in a game they're good at, and LOVE playing) is still available, they're not likely to give it up, even though little problems are encountered, and slowly getting worse. (weight gain and increased diabetes meds, or the occasional broken leg/arm from a bad landing under a tackle)
When it comes to choosing high carb foods, you also have the gov't, doctors, and food manufacturers telling you constantly that sugar won't hurt you in moderation (what is moderation? If you're used to eating 20 cookies at a sitting, and cut back to 10 cookies at a time, is that moderation? In the mind of someone who's used to eating twice as many, it probably is... and not merely moderation, but a white-knuckle inducing sacrifice), and that you NEED loads of whole grains daily (despite the fact that they're still 80-90% starch, usually with added sweeteners, to cover up the bitterness of the bran, and the rancid state of the oils in the milled grains.) So you congratulate yourself for doing the right thing, or at least the best you can do, considering that you've always eaten the cookies, and supposedly improved your diet by not only cutting back on the cookies, but also adding in all those heart healthy whole grains.
Basically, not everyone is even open to an alternative way of eating that not only forces them to give up every food they've enjoyed their entire life, but to also very blatantly go against everything that the gov't, food manufacturers, and their doctors have been drumming into their heads for the last 4 decades.
Those may not be the best examples of how I think this works - just the couple that I was able to come up with right now.