I carry daily, but generally don't have a firearm on my person when I'm at home. That said, my front door is down a flight of stairs, and there is a rifle just out of sight at the top fo the stairs.
As for the odds of needing it... well, they're obviously quite low. I live in a low-crime area and a large portion of my income goes to ensuring that is the case. Even so, my town (Charlottesville, VA) is currently in the national news because a college girl was abducted off the street about a block from my office. There have also been a handful of home invasion robberies in nearby towns over the past couple of months.
It seems extremely reasonable to at least have the option of using an effective weapon to defend one's self.
"Any" effort? You admit the risk is non-zero (and it's certainly a lot greater than that meteor), for me the effort is rather low, since I keep that gun handy for whenever I go outside and carry it concealed.
Let's add an additional dimension: this precaution is so easy it would be downright embarrassing to not take it and then get bushwacked.
I'd like to think the risk of killing an innocent is negligible. I'm neither morally or legally allowed to use lethal force unless I (technically a "reasonable person" https://en.wikipedia.org/wiki/Reasonable_person) believe I'm being threatened with lethal force and that's the best option.
My above testimony should be ample evidence that I realize the terrible responsibilities and consequences of using lethal force; I am therefore necessarily hesitant to do so, specifically my threshold is set high to avoid ambiguity. In my case, not having any dependents, and living with someone who's also capable of defending himself, I'm willing to take a certain degree of risk to avoid using lethal force on an innocent.
In this vague hypothetical, I might instead retreat into my house, perhaps warning the possible assailant that I'm armed and don't want to have to shoot him. Someone who (continues to) advance in the face of that (not to mention entering a dwelling with a strong anti-invitation) could be judged a threat.
Although not necessarily a lethal one, but if someone continues to advance on a visibly armed man, the man can at some point presume the one advancing intends to take the gun away, thereby posing a lethal threat. And all this leaves out whatever that person is saying, all part of his demeanor which one uses in judging his intent.
Holy crap. Do we live on the same planet? Being murdered by an unknown assailant who knocks on my door is so far down my list of risks and fears that it doesn't even register. I'm far more worried about being hit by a bus as I cross the street, or my car spontaneously catching fire in my garage. Sure, it could happen, but so could a meteor that obliterates my house, and it hardly seems worth any effort.