I don’t answer my door for anyone I’m not expecting. I say it’s for safety, which it technically is, but truthfully I just don’t want to deal with whatever they’re trying to sell or whichever candidate they’re trying to promote.
Whether I would knock on a stranger’s door depends on the situation. (And I’ll also say that I have the benefit of looking like a non-threatening, middle-aged white woman, usually with small kids in tow. I realize others will be perceived differently for their appearances and what may be a reasonably safe situation for me may not be for them.)
I’ve knocked on neighbor’s doors before, even if I don’t know them, to give them mail or packages that have been misdelivered. I’ve gone door-to-door in a foreign country where I didn’t speak the language looking for help after being stranded. I’m sure there have been other situations I’m forgetting.
I will say though, it’s not something I would do anymore without giving it some thought first. I think the increased use of cell phones along with a society that is… I don’t know, becoming grumpier? more distrustful? means people tend to first think the stranger at the door is there for nefarious reasons instead of innocent reasons. It’s disheartening to see how many posts make it to Nextdoor, sometimes accompanied by photos or video, wanting to know “Does anyone recognize this person? Why were they at my door?” For every person that responds that the visitor was probably just selling something or mistakenly at the wrong house, there’s another suggesting the OP should buy a gun and learn how to use it to defend themselves. Just a few weeks ago, a man posted that a woman rang his doorbell at 1am in the pouring rain saying something about “hospice” and her GPS bringing her to his address. He aimed his gun at her from the upstairs window and told her he was calling the police and she left. The 2-3 respondents who were horrified and tried to explain that she was probably an on-call hospice worker who was trying to get to a patient’s house were drowned out by the dozens of respondents who were overwhelmingly supportive of his actions and telling him that she was probably there to commit a home invasion, and that he was lucky to be safe. It’s scary.
So yeah, I might knock on a door in broad daylight in an area I’m comfortable in if I thought there was a good reason, but I’d avoid other situations if I could. In a true emergency, I imagine I would knock on a door because what other choice do you really have? But I would nervous about doing it.