And yet, statistically, caloric restriction has one of the worst success rates in modern medicine.
Depending on which study you look at, up to 80% of people who attempt lifestyle modification end up gaining the weight right back.
So yes, it's theoretically possible for everyone under ideal circumstances, but in the real world most people don't succeed. We can argue over why that happens - but the statistics remain.
So again... given these abysmal odds, for the 80% of people who try and (repeatedly) fail at lifestyle modification, what is the least bad alternative?