Let's take some very different situations. I'm walking down the street and see a remarkable moment between two people, or the face or the dress of someone that I find breath-taking.
I could stop, turn around, and catch up and say something like, Excuse me, but your expression, or the way your dressed, or ? looked so beautiful or stopped me in my tracks, or was so memorable, i don't think I'll ever forget it..... Begin with something honest about why you want to photograph them. We are then giving them respect and kindness, which is very rare in these days, especially from photographers. Then we might ask without intensity, "I'm wondering, would it be OK if I took your photograph?" That's about what happened with the two bikers. "I was driving by and saw how beautiful your red bikes look. You make an amazing scene. Would you mind if I took a photograph? I promise I'll be a quiet as a mouse." "Yeah, sure." No problem. But some people will say no and I just let it go. I say thank you, smile, and walk away. Maybe I leave with them a kind word or something that expresses, you look terrific.
In some cases, people have emmigrated to our country because if they stayed in their own country, they would have been killed. They will move away from any camera, so they don't endanger themselves or family that are still in danger.
It doesn't matter. What does matter is that I respect their wish not to be photographed, and move on with a smile and a kind word.
This applies especially in Ohio among the Amish. It is well known that to photograph an Amish person is offensive and disrespectful. So sneaking a photograph in any way, no matter how long a telephoto lens, is called stealing. I don't have to ask permission. I know the answer in advance. And I put my camera away in the car when I travel in Amish counties. Or I photograph landscapes from country roads, but never people. Stealing a person's image with a camera is an act of violence. But waving from my car to their buggy, passing by their buggy just a little faster than they are driving, is respectful and kind.
Yes, it's immportant and it really matters to ask permission, and sometimes we know ahead of time, the other person will not want to be photographed. Kindness, thoughtfulness, being neighborly, that's what I'm writing about, isn't it?