Because they're sickeningly sweet in a way that's offensive to the palette. They're basically almost like eating raw sugar, which is something even animals don't like to do because it's unpleasant. If people were designed to eat raw sugar in those quantities, we wouldn't bother mixing it with all this bitter shit, like chocolate (bitter AF in raw form), tea, coffee, or baking powder (also bitter AF and you can absolutely taste it if you forget to add sugar).

Like, even raw maple syrup or honey isn't as sugary as those cookies, and that's basically raw sugar in syrup form. I mean, again, at least stuff like honey or molasses have bitter-ing agents to make them taste GOOD and not just sweet.

It's an abomination of nature to consume that much raw sugar that way, humans aren't built to enjoy that.