Similarly, I don't understand why people answer the front door when they can hear or see (through peephole or Ring) that it's a stranger. I don't need your magazines, your house-painting services, your church, or whatever else. If you're lost and looking for your friend's house you're supposed to be at, sorry I'm not gonna be able to help you anyway.
Sometimes a neighbor you haven't met is the one ringing the doorbell.
I recently had to leave my car parked in front of a stranger's house, so I rang the doorbell to let them know, but they didn't answer even though they were clearly home. Capitalism might be great and all, but door-to-door marketing and phone spamming have killed reasonable methods of communication.
I refuse to let these things die, so I still open the door if I don't know the person (I have a hotel-like door latch now to help prevent someone from kicking in the door or shooting an arrow at me). You just have to learn to be aggressive and say "I'm not interested" if it's a salesman or Jehovah's Witness.
I've given them the "I'm not interested" line. They always still try to make their sale despite me repeating it. The worst ones are the guys going around trying to sell steaks or to look at your power bill to "save you money". There are also people around here that will give you a sob story about why they need the money to mow your lawn. I've lived in a few neighborhoods around here and it's always the same. If I want you over you probably can text me, so I just ignore the door.
Might not be polite, but I don't say anything to salespeople and Jehovah's Witnesses, I just shut the door in their face. They disturbed me in my house so I don't think I owe them anything.
Sometimes you have to be very persistent, and that gets interpreted as aggression. For religious cults, diffuse charity collectors and similar it's usually sufficient to politely tell them they've come to the wrong person, and to leave the building and never come back. The electricity and internet salespeople otoh are extremely aggressive and I have often had to shout at them or physically chase them out of the building, and threaten with law enforcement. They shout back that they're trying to do their job but I don't see why that should make a difference. I'm in Germany, for reference.
Are you suggesting the attitude should be to give your time to door-to-door salesmen and every religious organization that wants to convert you? Everyone who comes to your door deserves your attention regardless of their intentions?
It's not really an "attitude" as much as it is a solution to a problem. The problem is door-to-door salesmen (whether they're selling phone service, vacuum cleaners, Girl Scout cookies, or religion).
There are ways and places to meet your neighbors that don't revolve around knocking on my door unsolicited. Once we've met, you're no longer a stranger and the "attitude" doesn't apply.