1) Asking why someone does not have children.. 🌷
I see it is rude to ask someone this question because some people do not feel comfortable to say about that or they may have a healthy problem to have children and do not want to say. However, in some culture, they like to ask them this question which they feel you care about them and want to listen:)
2) Remarking about an obvious weight gain..🌷
I think it is rude because I do not like to annoy anyone by my words. Maybe when I will say, the person will be annoyed or low his/ her self-confidence, but for some people, they see it is positive to remark about an obvious weight gain to encourage them to lose weight! ..
3) Eavesdropping on a conversation..🌷
I see this behavior is very rude because maybe the speakers talk about something personal, and it is impolite to heard someone without knowing, but for some persons and cultures, it is normal thing!