Because the root cause isn't a sudden increase in appetite. What caused people's appetite to increase?
Pros and cons not withstanding, any intervention which reduces obesity is a solution. Think of it like having a flat and thinking that taking the nail out of the tire is the only way to fix it. Replacing the tire also works.
The problem with analogies like this is that they make no sense. A medication that suppresses appetite isn't replacing the tire.
Second, replacing the tire is worthless if the road ahead has another million nails on it.
It seems plausible that the introduction of evolutionarily novel ultraprocessed foods, designed by scientists in labs to be as tasty as possible, could increase a lot of people's appetites.
The processed foods however is what we’d want to get rid of. Otherwise all we do is slow down the loop, and add in more side effects.
Bravo. So we also know what we should go after instead of simply compensating the issue with new pills. Because we also know how well the pill approach worked in the US when handling pain..
So yeah, we could improve the future, but there's also lots of people who need help today and bringing up "but we failed in that one specific case" while being silent about everything else in medicine is silly.