It's easier to just stack those little bricks into a pile or kick them elsewhere. Consider however the strain on your pet's innards. Well, they do all that and more for your beloved pet. The explanation for including these usually is that they are fiber sources for your pet's well being. Maybe a little truth there but not the real reason they are added.
Whole grains provide great fiber content.
A bit of bran would do well too. The real goal is to make you buy the food again because clean up time is so easy and enjoyable with brand XYZ's designer stools. Before you do this to your pet, try it yourself for a few days. If the food is good and fed properly, stools will be fine without forcing your pet to work a brick through their digestive and excretory systems. First, the obligatory disclaimer.