You've obviously never dealt with a tweaker or anyone ballsy enough to break into your home, knowing that you can legally SHOOT them just for doing that, and decided to do it anyway. The problem with the logic of many law abiding citizens is that they think like law abiding citizens which is worlds apart from the thinking of people that would just as soon kill you rather than having to fight you in a court of law.
So someone breaks into your house at night. Their goal is to not wake you, get the stuff and get out. Advantage might not be in your favor - by the time you get your gun, get acclimated to the dark and awake enough to be aware the robber will either hear you and flea or aim. Locking your door, standing nearby with a baseball bat and calling the cops has a better outcome than firing at him.
Recently here in quiet old Eugene, two guys decided to rob a coffee stand at gun point. The barista drew his Glock and they started shooting at each other. One guy ran off, while still shooting at the coffee stand. The other guy stayed and fought, even though initially he had cover and was safe from the barista, he ended up being killed. The coffee stand employee DEFINITELY would have been killed if he was not capable of returning fire.
Or, had he never drawn, would have never been in that situation. He could have easily lost the gun fight.
Mostly I would say (like any competent firearm instructor) if you don't intend to use a weapon when it comes time, don't own that weapon. If you DO choose to buy the weapon, buy the ammo and learn how to use the weapon, that way YOU have the option whether you use it or not.
Again, 99% of the time nothing will happen. You're more likely to be killed by someone you know than a total stranger. There are VERY few burglary cases ending in murder of unarmed people (EDIT: Where the house wasn't targeted and murder already expected) - the goal is to get your stuff, not to kill you or anyone else. Homeowners insurance will cover loss. What's the most you could lose, and is that worth killing someone over?
The ammo industry wants you to buy their product so they love to share stories about massive gunfire battles to pump you up about one day being in a gunfire battle. It's no different than cigarette manufacturers wanting you to think their product makes you cool. Ammo makers want you to consume A LOT of their product at ranges in "training" for a battle that'll never happen. First off, most people just couldn't kill a person no matter how much they think they could. Second, most people will be too scared to fire accurately.
Police and military training aside, practicing shooting a gun is just a way to spend money on ammo and gun ranges where they display newer, shinier, bigger guns than you own. Yeah, owning loaded 12 guns makes your house SO MUCH safer than one gun or even a phone and baseball bat. Because when the time comes you'll be able to use all 12 together, right? Or you'll feel great about your kid pointing a weapon at someone and having one pointed back at them.
You're sold the fear of the drug induced black male gang member peforming a random break-in for the worthless junk in your living room, and then sold huge guns as a means to protect you from the black man. Then, lots of pretty ammo - because someone will make a decision to be hit based on what type of ammo you're using. Or they'll take the time to notice that your gun is a different brand and size than theirs. Here's a hint: getting shot by a tiny gun loaded with cheap ammo kills you just as quick as a bigger gun with the most expensive ammo.