Human Problems:

They throw away perfectly good food.
Humans think that chlorine tastes so good that they put it in the water.
When you offer to share your delicious, fresh bird with them, they say, "Bla bla bla have to clean it up bla bla bla bla..."
At times their minds are controlled by horrible space aliens that make them take you to the vet, who tortures you in ways that are, well... unspeakable.
You nearly kill yourself protecting their territory from a stranger-cat, and they reward you by taking you to the vet. (see above)
They would rather die than enjoy a refreshing, unchlorinated drink out of the commode.
They will not listen to reason. Some of my futile attempts:

"But Mrs. Smith, your parakeet was dead when I got here. I did you a favor by eating it!"
"Pardon me, Dr. Veterinarian, but if you touch me, I will kill you."
"I share my fresh mice with you, you share your roast chicken with me."
"Those lumps in my litter box are not going to remove themselves."