We have four cats and we feed them wet cat food exclusively except for supplementing with ham or fish. They have water to drink but we have NEVER seen them drink it. Why would that be?
Well, it's because all felines have a very poor drinking reflex and get most of their water from their prey, or in our case from the tinned food which is 80% water (I know!)
Cats and dogs are different in the way they handle carbohydrate. Cats are obligate carnivore in that they HAVE to eat meat. Dogs lean towards omnivore lite and can handle carbs better. We have all seen adverts for dog biscuits, but you will never see ads for 'cat biscuits'. But if you are feeding your pet cheap cat dry cat food that's exactly what you are feeding it. Throw an arrowroot on the floor and it will be ignored, but soak it in meat juices and...! The ONLY reason dry cat food came about is that meat is expensive, wheat, rice etc is not.
So, if your cat, and let's face it, dog, has a staple diet consisting mainly of carbohydrate it is on the road for obesity, diabetes and ultimately kidney failure and death. Having been there in the past I cannot emphasise what a horrible death, preceded by utter misery for you both it is and a pointer to us as a species who are, as a world wide society, on the same path.