Many decades ago now, when learning how to shoot and care for firearms, my father never used one, so I've never used one. Always seemed like a solution in search of a problem to me (nobody I know of my age or older who grew up without even the idea of one ever seems to see any sense to them, and nobody I know with military service ever used one either, which includes some who shot competitively while serving).
I do only use brass cleaning rods, not steel (and bronze brushes, never steel).
I use them on all my bolt rifles, and the AR-15, since hinging the action allows me to insert a guide as opposed to other types of semi-autos where you can't get one in. Not so much a chamber saver but to prevent wear on the leade and start of the rifling. Also tends to keep solvent and gunk out of the action, but usually clean the inside of the action anyway before I'm done.
If I'm going to clean a gun with a rod (vs. a Snake or something), and if I can do so, I'll use a chamber/bore guide. I use the ones from Sinclair made of UHMW. I have a couple of 'universal' ones, but they don't really seal anything, whereas the Sinclair ones do a pretty good job of sealing (so that cleaners, oils, and crud don't flood the actions).