It sure slows down fat accumulation but has other functions too, like not getting so full you're not able do anything else than digest food.

Also there are plausible reasons why you would eat past satiation. Satiation is not necessarily the same thing as not getting pleasure from eating excess food, especially if you live in an environment where food could become temporarily scarce.

I also talked about satiation here, and don't find attacking this issue just from a single angle at once useful.