Some reasons:
- All my aging relatives are in China, so I just don’t know many old people in the US
- China has more people and a more public way of life, so I just see more on the streets of China
- I live in a part of the US with younger demographics

Yay for new comix!
I live in a part of the US with older demographics, and I don’t see old people out and in public either, except in shopping centers and restaurants and so on. But then, I don’t see anyone out and in public except in those places because my town is a suburb without an urb. People have homes and they pretty much stay there except when they have a reason to go out. It’s sort of sad when compared to your illustration of Shanghai.