I'm not a mother. I was wished a Happy Mother's Day by a stranger today. I said I'm not a mother. Then he said well happy Ladies Day. I get mildly annoyed when people do that and it's only men who seem to do it. It's happened several times through the years. Don't assume that just because I'm a female that I have kids. Only wish people who you know are mothers a Happy Mother's Day. I don't go around wishing random strangers happy Mother's or Father's Day I don't know them.
No it is not only men who do it. I agree with you about not saying that to people you do not know or people who aren't your mother. Years ago I worked retail and some idiot wished me Happy Mother's Day. I kind of went off on them. NO it is not a HAPPY Mother's Day for me. I am here and not with my mom on Mother's Day.
Also I remember being in Dollar Tree the Saturday before Mother's Day and this lady was buying the fake flowers. Some foolish person is like oh Happy Mother's Day. At which point she lost it. I knew who she was. Although did not know her personally. She was buying flowers for her daughter's grave. Her only child.
I don't care if the person has kids or not if it is not your mother or close family you should not say that to them.