I could eat cereal for every meal and a decade ago every single person in the country ate cereal for breakfast? Yeah, that's a distant memory now.
Americans just aren't that into cereal anymore. And it's not a low-carb thing . . . come on. We love carbs more than ever. It's just that for breakfast, we now prefer things like bagels, Egg McMuffins, pastries . . . stuff we can grab and eat on the run.