Don't get why people do that. I propagandised it a lot when i got on GLP and keep telling people how it changed my life (and how it didn't, too).

Most people operate on feelings, not reason. Thus it is most likely out of shame born from supplementing for lack of willpower by using drugs.

Eliminating sugar from diet, shifting from carbs to fats or intermittent fasting will all have a greater effect than these drugs. But they all require some willpower at the start; Discipline, which people seem to lack.

Alternatively, a more rational take is to consider "crabs in a bucket" mentality. Awareness leads to not publicizing your personal goals and how you're working towards them.