The problem with appetite suppression drugs is that they simply make you not feel hungry, but do nothing to fix your lack of discipline and self-control, I'm sure most people who lose weight on these drugs, and then come off, will just go back to their bad habits.
So why not just stay on the drugs?
You technically could but the idea here is to cut the excess bodyfat percent and get into the healthy range, rather than to keep losing weight, which itself is also unhealthy, but once you become dependent on the drugs to maintain your weight, without fixing your habits, you will just go between getting off the drug, binge eating, gaining the weight back, and hoping back on the drug and losing weight while barely eating, I can't imagine bouncing between such two extremities being good for your health.