A good guard will prevent kickback and thus save you from injury. Fingers are an obvious risk of a say (and such accidents happen all the time), but kickback is the larger danger and the right guards will prevent that.
On my consumer grade Dewalt, the blade guard, riving knife, and kickback guard are all separate components, so I guess I was considering them separately. I still don't trust the kickback guard fully either, so attempt to stand off to the side if possible if I'm worried about kickback.