I've been nearly every size... I think it's a backlash against all the obesity/disease awareness.
Based on the people I know... Obese people hear all the time about how they are outside the typical standard of beauty. Now they have to hear about how unhealthy excessive fat tissue is in the body. Instead of hearing the health warning as it's intended, most hear it as "fat people are bad and ugly" in a sweeter package, and how horrible they are for making fat kids. They feel bad about it instead of feeling motivated to do something about it.
I think this curve BS (and I thought it was BS before I just lost 50lbs) is their way of feeling better without having to do better. I have mixed feelings about it. I think regardless of what size a person is, they deserve to love themselves and be happy in their skin. At the same time, I think "putting honey on thorns" and giving rolls of fat the new name curves is delusional. Even I can tell my rolls from my curves.