As you point out, it's also not about the effort. It's also not just the lower class that is effected. It's a problem at all socioeconomic levels. it's just much easier to hide it the more money you make.
It has nothing to do with not wanting to work. It's about not being healthy.
We do not optimize for health in this country. We optimize for profit making. It's not surprising we are massively unhealthy. What is perhaps surprising is that we're so stuck to the idea that profit making is the most important thing to optimize for, instead of individual health.