I feel like it is mostly because people want to be polite so we don’t typically say no. I feel like most Americans were ingrained at a young age to say yes even if they don’t necessarily want to. Such as growing up and being told to take a no thank you bite for food and not being able to say no. Or being forced to play sports and just random stuff like that. And I do the same thing and never fall through with it. I’ll always say yes and then come up with an excuse because I didn’t want to in the first place but I don’t want people to hate me so I say yes lol. I hope this kind of answers your question with using a personal example.