There is theory, and then there is practice. A 300lb person will have trouble just "eating less" and "working out", because both of those things put incredible stress on a person's mind and body. Immediately working those lifestyle changes into an obese person's life is not like flicking a light switch, even for the overweight person who looks at themselves in the mirror and cries about how they look, "just eat less" and "just move more" are ideas that are psychologically difficult to put into action.
With GLP-1 medications, it is considerably easier to do the first part of "eating less". An obese person can lose over 20% of their body fat in a year, which will reduce the probability of injury when they begin working out. There is hardly any downside to developing medication to help people manage their weight to below obesity, and incredible upside.
Maybe another example would be: why do you use VSCode to do your programming? Hell, why do you use a computer at all? You should probably do it the hard way, on a sheet of paper... there is no reason to use a keyboard when you could just use your hands, right?
GLP-1 agonists are just tools like anything else. They make difficult tasks easier.