You need to remember that people experience reality differently. For you eating the healthy number of calories may be easy. For others it very much is not. I have heard it described as leaving your thermostat at 45 in the winter to save money on your gas bill. Sure, you could do it, but it would cause a lot of suffering. GLP-1s are able to change the way people experience hunger so that it only feels like the thermostat is at 65 instead of 45.