I disagree with this. We used to feed our cat wet food and thought nothing of it, until her first yearly checkup and the vet carefully broke all the tartar off of her teeth. He recommended Royal Canin dry food and gave us a sample pack. The cat loved it, as and it was only available from the vet I expected it to cost the earth - it actually works out £7 a MONTH which is a pleasant surprise.
Every checkup since she's only had minimal staining to her teeth so we now have cat toothpaste to give her twice a month which you just squeeze a blob onto her paw and she licks it off.
She drinks plenty of water to compensate for the lack of liquid in her food but that's to be expected.
Todge already took the words from my mouth. I'll expand a little, if you're interested...
All of the "prescription" dry foods that you can only get from the vet are a huge con. Oral care, hairball relief, weight control, etc, etc. It's absurd, really. The shape/size of the kibble has no benefit to oral care - and that's all there is that makes it "oral care".....I've compared one manufacturer's oral care food to their regular food and it's identical apart from the size of the kibble. Hairball relief just means it has slightly more fiber in it so that the cat poops more often. In other words, none of the prescription foods have any medicine in them - it's usually tiny differences in the ingredients and clever marketing.
So why do vets sell the stuff? Firstly, (and I'm talking from my experience in the US, maybe it's different in the UK) vets are surprisingly ignorant about cat nutrition. They take a general small animal nutrition class during training and that's it. If they want to learn more about cat nutrition it's up to them to do the research themselves. Secondly, the big companies have a vast network of sales reps that hit the vets and give them all kinds of nice incentives to sell their product. So the pet owner is given the "special" food and thinks "my vet is an expert and knows what he's talking about" - which usually isn't the case. I'm not blaming the vets either - they have to know a huge amount....one minute they're treating a cat, then a gerbil, then a budgie, then a horse, then a stick insect, etc, etc. They can't be an expert at everything (some do specialize of course) and the prescription food is an easy option that reassures the owner that their pet is being looked after.
As for dry food in general - just look at the ingredients in that Royal Canin dry food. Apart from the dehydrated meat everything else is grains. Cats are obligate carnivores.....their digestive system can't do anything with grains apart from poop them out. So why not just give them proper meat?
) and another £10 quidco cashback. All with free delivery too. So works out to about £19 per cat per month for what we feed ours. Thus far I have about 7 different accounts with them lol.