Because they don't have that "we" factor that humans have? Kiba ate her own puke before AND our cats as well....gross!!! It's not uncommon for them. But we try to stop it and clean it up first. Maybe do a quick sweep of your house to make sure it's puppy proofed? So no hair ties, pens, papers, or anything else she can get on your floor. Kiba will put everything in her mouth and has if we aren't careful. Lol. I've dropped earrings and various other stuff and she's quick to get them.