Obesity is a disease. The AMA says it, the insurance companies say it...etc.
It is multifactoral in origin.
But once someone is sufficiently metabolically deranged as we are as morbidly obese people, the chances of "doing this on our own" are as slim as winning the lottery. The surgery is only a tool that helps break the metabolic/hormonal cycle that drives obesity. But like any tool, it will only work if applied correctly.
A hammer is a tool. But it will only drive the nail that holds up the scaffold, if you pick it up and apply action and the force of your determination. Same thing with the whole WLS stuff. You HAVE to change your behaviors with food in order to lose all the weight you want to lose. It isn't magic bean surgery. And that goes WAYYYY beyond just "mystically, magically learning how to eat small portions." There will come a day when you CAN and WILL eat again--more than you should--of things you should not be eating. Life will get messy and in the way. And there is no operation in the world that will healthfully keep you from eating your feelings unless you do the hard head work involved.
WLS is a tool to help put morbid obesity into remission. Once ANYONE is morbidly obese, you can consider yourself to have an intractable, incurable, degenerative disease. But, with the surgery, and with proper attention and care and help, you can put it into remission.