Dry food has no moisture in it, and includes lots of garbage filler like ash and other byproducts. Cats are desert creatures who have evolved with little instinct to seek distinct water sources. Most of their hydration would have come from prey liquids like blood. Without it, cats are slowly ticking kidney failure bombs. I have given mine wet food for years, and at 15 they both physically look no older than 4, kidneys in great shape, have been able to skip dentals for 2-3 years because their teeth have been in such good shape. One is getting a dental in 2 weeks because she may have a fissure in a tooth, unrelated to generic tartar build up. Vet broke a bit of tartar off the other with her finger and joked that was his dental for the year.

On the other hand, every other cat I’ve had was raised on dry food only and all were dead by 4-10, except 1. I’ve had many cats. Shame I was a child for most of them and had no control over how we fed them.