If they lack the motivation or determination to see through a diet, that's on them. The resources to count calories are there, it's not nearly as hard as it would have been 20 years ago.
Now, some people genuinely have some form of disease or unusual case where medication is 100% needed and no lifestyle change would help - and those people should get whatever treatment best suits them.
But 36% of the US (obese) is not an unusual edge case, some rare genetic disorder or disease.