Theres some failure to imagine situations outside your personal experience here.
A labrador walked on pavement probably will self trim except for the dew claws and some will nibble them down themselves. One of my dogs does this, she chews down her own claws or they're taken care of by pavement walks.
Two of my dogs do not - they both have rather flat feet and the nails grow almost straight out, not down to the ground. Combine that with much of our walking being on soft grass/forest floor, and their nails NEVER get worn down and easily over-grow. So I clip them myself, but then I have a grooming table and I taught them from an early age to stand on it or to lie upside down in my lap for that.
My partner is absolutely useless at nails, hes terrified of catching the quick so is quite panicky about doing it and as a result is more likely to catch the quick or worry the dog - he would be better having a groomer do it.
Some dogs coats really need a proper bath, blaster dryer to remove undercoat, professional dryer etc, or they will take DAYS to fully dry. Lots of the very popular poodle mixes fall into this category, having coats the owners were not expecting/could not predict.
I wash our hound, he is a stinky bastard if I don't and no amount of brushing fixes that, he dribbles on himself and delights in developing revolting stalactites round his face-flaps. It's only once every six weeks or so, and he is outraged by it but also really likes the treats and also the paw massage (getting the matted bits of crap from between his pads) that goes with it!
I have taught my dogs to enjoy grooming though - many people don't bother, assuming that the groomer will do it and that is unfair and unkind, and leaves dogs suffering. Of course the groomer says 'Oh yes Fido was fine' to their client... unless Fido has actually taken off a few fingers... because they know thats what the client wants to hear. They'd have no business if they said 'well actually, Fido was fucking terrified, tense and uncomfortable the whole time and we did worry at one point if he'd have a heart attack in the bath, he also tried to bite a few times so we strapped his face shut and suspended him in a sling so he couldn't throw himself around'...