One more thing it prevents. I gather from folks who've pulled stuck bullets the old fashioned way that that process often takes hours or days, or longer.
There is a problem with that, in my opinion, that goes beyond inconvenience. A hung-up ball that ends up taking hours or days to get out is a STRONG temptation to leave a loaded gun around. In fact, I'd hazard the opinion that many people who find their shooting session or hunting trip interrupted by a ball that won't fire will, of necessity, find themselves lacking the necessary hours to get the ball out.
The result of this is going to be a gun sitting around with a charge in it--even if you're an otherwise-safe shooter, you just may have no choice; it gets dark, the range closes, etc., etc.
Now, life has a way of marching on, and it's easy for that "I'll-fix-it-when-I-get-home" project to turn into one more of those "I was going to get to it but never had time" projects. Two months ago, one of the guys I work(ed) with dropped dead of a heart attack, at age 55. No warning. We're still cleaning up the projects he left in various stages of completion.
This was much on my mind when I realized that a secondhand muzzleloader I'd found turned out to have an obstruction in the barrel about 2 inches in front of the breech. Loaded? I couldn't tell. I certainly didn't have the time to drop everything and spend half a day pulling a ball. And the thought occurred to me: what if I had an accident, or a heart attack, and that barrel were found by one of my little boys ten years from now, when they're capable enough to know what a rifle barrel is, but not yet wise enough to foresee all the dangers. What if they, like the pawnbroker who sold me that gun, didn't think to run a ramrod down the barrel and see if it were clear? What if they downloaded the instruction manual from the internet and saw where it says to fire a few caps before loading the gun for the first time, to ensure that the fire channel is clear? If an unpulled ball is an accident waiting to happen, isn't it incumbent on us to resolve such things before forgetfulness, mortality, and/or busy schedules turn our problems into other people's problems--possibly the problems of other people who may or may not have the sense to deal with them?
This is what prompted me to get, and use, a CO2 discharger. And in under 5 seconds, a potential trap for who-knows-whom was resolved and rendered safe. Hard to beat that, eh? If I'd had to wait until I could make time to pull a ball the old-fashioned way, it'd potentially become a safety issue down the road, even decades later.