Maybe you can titrate off the drug and in a perfect world, the hunger signal doesn't come back on all the time; that'd be great. Maybe, while on the drug, you've developed eating habits that you can continue while off the drug, even though you feel hungry all the time, again. Maybe, it's just too hard to ignore the hunger signal, and you need the drug for a lifetime.
That's not to say these drugs are necessarily wonderful. Previous generations of weight loss drugs came with nasty side effects that weren't immediately apparent. Fen-Phen was a wonder drug until it ruined people's heart valves. Stimulant appetite supressants have issues because they're stimulants. Cigarrettes have appetite supressant properties (not surprising, nicotine is a stimulant), but they're cigarettes.
Personally, I don't have an overactive hunger signal; so when I eat poorly and gain weight, it's on me. But other people I know have a totally different experience with hunger. If your body is telling you all the time that you need to eat, it's hard to say no. Just like it's hard not to scratch when your skin is itchy. I can resist itchyness sometimes, but when it's constant, I'm going to scratch.