There's hardly a moment when a dog is handled as completely as during grooming. Every paw, both ears, the belly, the skin under the thick coat. You rarely get that far with a cuddle on the sofa.
That's why grooming often turns up what otherwise stays hidden: a few black specks that turn out to be flea dirt, a red patch, or a lump that wasn't there last month. Usually it's harmless. Sometimes it's the reason for a vet visit that comes early enough.
Then there are the nails. Many people treat the clicking on the parquet as an everyday sound. It actually means they're too long. Left that way, they can curl, hurt when walking and press on the toe joints.
Ears are more interesting than you might think, too. A dog's ear canal runs down and then bends sideways. Whatever gets in has trouble getting out. That's why dogs are so prone to ear infections, especially those with floppy ears.
Perhaps the most important thing about regular grooming has nothing to do with the coat. A dog that knows grooming as something ordinary stays calm through it. A dog that lands on the table once a year with a badly matted coat goes through hours it doesn't enjoy, and remembers them. A small knot is quickly undone. A matted flank is not.