By themselves, without commitment and real lifestyle change, I agree.
But as a boost, or to help one get through a rough patch they have some value, in my experience anyway. Given the 'growth' of the market it seems inevitable that they'll get better with time too.
But even the most drastic surgery, a full Roux-en-Y gastric bypass can be eaten around by somebody who doesn't make the commitment to a new themselves.
For those that are ready and commit though, anything that helps them along by helping them stick to it or by boosting the results (helping the person see progress easier so they *stay* committed) can only be a good thing. Except when it isn't, like Fen Phen...