Hi Mordrid, well I figure that it's the closest to the cat's natural diet. I have seen what dry biscuits can do when feed by themselves to some cats. One cat I know of used to scream in pain when urinating and I told the owner try feeding the cat some wet catfood, instead of dry.
But first, they went to the vet and the vet insisted that they should keep feeing the dry cat biscuits (vet ones) and the problem continued and the vet was pretty much giving "medicated" solutions and leaving the cat in misery.
Finally the person in question decided to try wet cat food (just orindary canned) and the problem came right. Cat is happy

It is not natural for cats' to exist on dry biscuits in my opinion....Though I did feed good quality ones to my cat, mainly she did well on raw meat. Again, it's more natural for them. Cats who have been brought up on dry food or canned food, may take a bit of adjusting and it's probably wise to introduce a bit at a time, whilst you lessen or phase out the other.
At one stage, after my cat had been hit by a car, she became anorexic because of the internal damage done and loss of appetite. I was in tears. she would not eat anything I put in front of her and was becoming thinner all the time. ONe lady suggested I try feeding her "gravy beef" (which is just cheap cuts of beef). I cut it up for her and she ate it and began to put on weight again. She was always fussy though and it was hard for me to get her to eat anything, but raw food usually did the best.
I did vary her diet though and she had some canned and dry food too. In hindsight, I'd have fed her mainly raw if I could go back because I think they put stuff in the other foods that could build up in their system and cause problems with kidneys/thyroid perhaps. Just my view. I could be wrong.
She died at age 14 after going to the vet and being vaccinated by an incompetent vet, who I think gave her too much (she wound up with a disease - the bone in her front leg began to enlarge to where she started limping) and then medicated for "thyroid" issues, to which she then went blind, they then put her on blood pressure drugs to try and reverse the blindness and she stopped being able to walk properly or feed herself and the issues were then irreversible. Admittedly she was petite and ageing, but they absolutely finished her off and for a hefty sum of money too. I then had to have her put down. When I laid a complaint to the vetboard, It was pretty much made out to be my fault. They well and truly shifted the burden of guilt onto me and told me that I had been offered more help and I finally refused......um when your cat is pretty much dying after all the medicating, would you let them continue? She was so far gone, I had to feed her by hand, because she wouldn't get up....she only forced herself to move when she need to go toilet. I finally took her to her to the SPCA animal shelter, the guy told me "This cat is too far gone". He was quite surprised at the bone in her leg and I said to him, she had no sign of a problem until after vaccination and overnight stay at the vet. Came back next day and was not the same. She wound up blind, crippled and miserable/depressed after what they did.
So though I had her vaccinated in the past, without issues, obviously the last vaccination, done by a vet who I feel is incompetent, she just didn't come out of it normally....whether it was her age, or he overdosed her, I don't know. She was kept in overnight too for thyroid tests, so who knows what happened to her? I collected her the next day and she wasn't the same. Very quiet and kept holding her front paw up. Later of course, the bone started enlarging and then of course, after thyroid meds, she went blind and the rest you know.
But I can tell you this. Before all of that? That cat was a ball of ongoing energy and I attribute that to her diet, which was mostly raw meat. I also gave her the odd raw egg mixed in some milk. However, I do feel water is the best daily, but the odd milk/egg drink she loved.