Does it not work well? Before GLP-1 agonists your options for weight-loss drugs were pretty limited. Stimulants work well but they have lots of side effects, put much increased stress on the circulatory system, and aren't sustainable long term (also extremely difficult for working people to obtain in the age of the drug war). There have been other weight-loss drugs but many have been withdrawn because of the risks associated with them.

As far as I know, GLP-1 agonists are some of the most effective and safest weight loss drugs discovered so far

As long as we live in a slop-based society where it's completely on the individual to not destroy their body with the garbage food available I think these drugs will be quite popular