Depends what you class as clean. It doesnt replace your usual shampoos. Its an extra stage to soften traffic film and larger debris and you rinse/jetwash off before moving in with the mitt and shampoo resulting in less “muck” on your vehicle for the contact stage so less chance of swirls. Having used various snowfoams and selling them, I would estimate even the best snowfoams only get rid of approx 1/3 of what your mitt (or sponge if your into self harming) does but with next to no damage where as no matter how careful and great your technique and products used are, theres always a chance of scratching and swirls when your moving something against the paintwork.
Secondly though, and most importantly for some, it just looks cool.